The Sten was meant to be dropped behind enemy lines to arm resistance forces. It was also designed to be cheap and easy to build, most of it could be replicated by water pipes and sheet metal.
It was actually a major inspiration for the M3 "Grease Gun" that would supplant and replace the Thompson in the coming decades. Though, harder to make and far more reliable than the Sten.
Yes. A working variant of the STEN could be created without welding, allowing guerrillas to easily construct working weapons from even places like bicycle shops and facilities with limited tools and equipment. So existing guns could be dropped behind lines or new ones made on the ground. The Tommy was a fine gun and had better performance in several areas to the STEN, but the costs of the gun and the realities of combat led the allies to create their own cheap submachine gun (the m3) and even the Germans used and made STEN machine guns to supplant the costly and more complex mp40- with the German MP3000 being a Sten derivative.
The STEN and various version survive on to this day as with the M3 with various countries and private users. Much like the AK series and related weapons, it may not be equal to more complex weapons on paper, and may sacrifice some real world absolute performance, but the longevity, reliability, and the ability to easily and cheaply outfit armed forces are distinct advantages in war where 1,000 zip guns usually trumps an army with 100 top tier weapons. Likewise, things like absolute accuracy often aren’t critical to general infantry so much as reliability when it comes to real world performance.
It was actually a major inspiration for the M3 "Grease Gun" that would supplant and replace the Thompson in the coming decades. Though, harder to make and far more reliable than the Sten.