I’m not sure about less quality, but having a matching treble character and general dispersion and compression characteristics are important.
WHY we often get smaller subs though is usually due to size and money constraints. Not everyone has the room for 5 full size floor standers, and small surrounds are really convenient with subs. Imagine getting super expensive main speakers for stereo, and then more than doubling it for surrounds and a center.
Some manufacturers used di-pole surrounds and those were often even more expensive than the main satellites.