Open Baffle. Why are they mostly limited to DIY?

Open baffle combo guitar amps and speaker boxes have been around seemingly forever, and I prefer them over closed boxes these days, except for bass amps.

Another reason not mentioned is the imaging...most prefer what they know and an instruments sound, in stereo world, that seems to not come from a particular point bothers some...or at least i opine. i enjoy my 12" audio nirvana f.r. ob with a sub... i know its not high end but i think the sound is very lifelike with the music i prefer.  We have been sold on the idea of exact focal points and tbh in many live situations the sound is not at all 'stereophonic'. the return is correct time/phase alignment and a small set tube amp is more than enough. ymmv

Alon, Nola have been around for a while also.  You can build your own field coil speakers and they will sound fantastic!

I stopped into the DIY room at this year's Capital Audiofest and they had a low-powered tube amp driving an open baffle pair of DIY speakers, with a 12" Tannoy driver facing the listener, and an 18" down firing driver for the low bass.
I was really impressed with the sound they produced!  I asked the builder what he had in them and he said "about $1700", and further explained that the only reason the amount was so high is that Tannoy apparently doesn't sell individual drivers, so he had to purchase a pair of their speaker and remove the drivers from the cabinet.
Very impressive sound!  Even more impressive for the price!

I have a pair of Spatial M1 turbo and must say they are not power hungry! I am fan of concentric twitters and I like the bass too ! The only thing with OB is the size of drivers and not very dense sound like high end speakers! I think you should not judge OB speakers if you have not heard any good one!