Some materials need a heated chamber, which in itself is an enclosure already. However materials such as rPLA, PLA, PHA don't necessarily need a enclosure, or even a heated bed.
Could printers that only print with such materials still benefit from print enclosures in terms of print quality?
Also, are there other reasons to put printers that use only such materials inside enclosures?
This is one of those "yes, if", or "no, but" situations.
The short answer is that if you have a printer that is only being used for a material such as PLA then the average user will see no advantages from having an enclosure as they print perfectly well at ordinary room temperature, and slight variations in temperature have minimal effect because they're stable and don't warp or shrink very much.
You can probably stop reading here.
Even for printer businesses, most PLA-based print farms use basic open-frame bed slinger-type printers as there are no benefits to enclosing them, so it's not worth the additional cost.
If your printer is in your bedroom, the only advantage that an enclosure would provide you with PLA is that it would be a little quieter.
The exception to this is if your printer is in an area that has high temperature variations, or high levels of humidity. For example, my 3D printer is in a room with two pottery kilns and a wood steamer. Or it being in an outbuilding where it gets down to double digits below freezing.
Some materials don't require enclosures for quality reasons, but having one with proper venting is a good idea due to the fumes that they give off. However, this isn't an issue for most people as these materials are less common.
