Are side firing woofers only for aesthetics?

Like everything else in audio the particular design is everything. Speakers like Audio Physics do very well with a side firing woofer that otherwise would not fit the cabinet. A narrow cabinet has less diffraction effects than a wide one so there are sonic reasons to use them but they are not in themselves better or worse than front facing ones. Less diffraction but generally harder to place in room due to more complex radiation pattern.It all boils down to whether you like the sound of a particular speaker, the design parameters are secondary.

Actually it does have a lot to do with the ear's ability to localise the position of a sound source.I would also think with all drivers firing front.You would have to listen further back then side firing...just my take and if wrong I stand to be corrected..always willing to learn.

As one responder wrote, they should image better due to a narrower front baffle. That said, the speakers I've used with side-firing woofers have been a bit problematic in the bass in my rooms when speakers with front-firing woofers have worked better. And I'm speaking of the VMPS RM30's, which were less problematic than the Audio Physic Virgo II's I had in a smaller room. Both of those have side firing woofers but the Virgo Woofers are crossed at around 600Hz (fairly high), and the VMPS around 250Hz (worked better).

Speakers with down-firing woofers have worked well for me. My NSR's have a down-firing woofer, while all my others are now front-firing, including a pair of VMPS RM2's. The dipole Maggies fire both ways but also seem to work well for me.

Mechans,
My Coincident speakers are narrow profile with side mounted woofers(2x 10 inches per side).In my room they work just fine and very often totally seem to disappear. You also have the option to face the woofers out or inward depending on preference and room.I`d give a very positive yes for this approach.

I currently own 3 pair of floorstanders with side firing woofers(Canton Karat M-70,Coincident Partial Eclipse,& Infinity Kappa 400).This configuration works well in both rooms where I listen,even though placement is closer to the sidewall/corner than I would prefer.As Charles1dad said,the ability to place the speakers with the bass drivers facing inward helps.In other rooms the opposite may be true.