Now here's a revolutionary idea

But regardless of being an adult or not- it’s advised that acidic or sugary beverages be sipped through a straw anyway, and people with dental sensitivity of some sort (1/8 are reported to suffer sensitivity- aka 12.5%- aka many) can find it painful or uncomfortable to not use straws- especially with cold, hot, sugary, or acidic drinks. People with dentures or other prosthesis or veneers can also benefit from straws. So overall the straw can certainly be said to offer practical benefit to many people.

And that's aside from the fact that a lot of straws are used for convenience. The average person could definitely drink without a straw while sitting down at a dinner table, but change the situation to walking down the street or driving a car, and the difference between straw and no straw prevents spills and potentially traffic issues [especially foot traffic issues, where people keeps stopping to drink in the middle of crowded sidewalks].
I think everyone should make a conscious effort to make good choices for the environment, and not using plastic straws is a good idea. However, a vast majority of pollution comes from companies, and the biggest impact the average consumer can make actually comes far more from making response choices in who they buy goods from and what industries are supported than what product waste they create.
And yes, paper straws are pretty terrible. But metal or silicon reusable straws aren't actually bad...

... and the silicon ones aren't usually a problem for people who bite their straws the way metal ones are.
So, all said I think the best plan is reusable straws. And moreover, making good choices about what industries you support. If reusable just doesn't work with your lifestyle, and you don't want to use paper straws for texture reasons, they do make straws made of plant "plastic". They are compostable, which I realize won't prevent them from filling up landfills. It's just better to use the plant plastics than to use petroleum based products.

It is a good point- and let’s examine it- what are you drinking to begin with? Soda, most juices, alcohol? None of these are “good for the environment” even if we ignore personal health. All of them use a tremendous amount of water and energy to create as well as creating waste. Major battles against drink companies in many countries are over the fact that much of the world still has shortages of potable water and these bottling plants use up water that the local population needs to survive and or grow crops. Speaking of crops- mass commercial farming is a major source of ecological destruction. The majority of rain forest and food crop lands cleared and converted to commercial farming isn’t for meat or timber but for agriculture.

The techniques of such farming require again- massive amounts of water, pesticides, and commercial fertilizers which no only polite through their manufacture and transport but they leech into soil and cause things like algae blooms and ecosystem devastation as run off into local water habitat. Huge amounts of grains that could feed starving people all over are then converted into beverage used for no nutritional reasons but only for pleasure. It goes even deeper..... because just because you aren’t drinking from a plastic cup or bottle- maybe you’re even using a bio degradable cup or reusable? Well.... that drink still likely cake through a container of some sort. A fountain bladder, a plastic lined metal tank, from a machine with plastic lines etc... paper this and that... all the stuff you don’t see so you don’t think about.

And so my point is... a little better is always better than nothing- but the movement to vilify the straw and it’s users is ignorant but well meaning. You see the straw so you say “this is something I can do to help...” the assumption is that a straw is a simply convenience or pleasure that can be given up. But... so are soda and beer no? Ah. But giving those up would really effect some people and their enjoyment of life- but it would make a much larger impact and drinking water from a glass water bottle doesn’t generally need a straw does it? So now you’ve cut out a great deal of those nasty destructive things you don’t see haven’t you?

I’m not shaming anyone or saying you should go to the extreme (although honestly we all probably should- but I don’t plan to...) but over all we can’t really be too hard on the straw users in our midsts because the burglar and the pickpocket can’t really judge each other nor be objective about their crimes. Of course- while the world is fighting the evil of straws we are conveniently (for those concerned) busy legislating and shaming each other over straw use instead of demanding that maybe nestle knock off the child labor and let people have water, or that coke maybe also let people have water and stop murdering union members- or that any of them maybe make small changes that would reduce their ecological impact by hundreds of times the amount that giving up straws can do. But- the greatest trick the devil ever pulled was to convince the world he didn’t exist.