I would guess because most cant afford or have ability to have quality time with 30 amps or 50 effects? Seems reasonable.
Oh for sure...buying one modeling box VS 30 amps is easy math. That said, I don't think it's all about the money. I mean, there are guys who can afford 30 amps or even more, but I think most of the time, only a few are getting played regularly.
While 30 amps is way beyond my budget...I have 8 of them in the studio right now (I think I've had a total of 15 or so different amps in my lifetime)...and right now, I'm trying to unload at least 3 of them. Why..?...because they don't get played.
Not because they suck or anything, but because I found 2-3 amps that give me the tones I want, the tones I've been after over the years. The others are great amps, and to someone else they might have the right tones...but I'm just not using them.
IOW...I never go through all 8 amps when I'm going to do some recording, just because I have 8 amps...and if I had 30, I would probably still focus on the 2-3 that give me the tones I really want.
I'm just saying that I think (I may be wrong) but that many players are like that...they find their tones, and that's it. Sometimes you get the itch to try something new, but if you really have found your tones...you just keep going back to them.
Now if you're still searching for your tones...then keep auditioning amps.
That said...from a studio production point of view...the modeling box, loaded with amp sims, is certainly a sweet "carrot" for a busy studio and clients that want to try out a new virtual amp, or who are undecided on the tones they want for the session. If I was running an open door studio...I would consider it, 'cuz I got no more room for real amps!
Besides my "tone hunt" over the years...one of the reasons I kept buying and keeping amps was because of the thought of doing more outside recording, and having more choices for people...but I didn't really pursue that course, so now I want to unload a few of them...make room for some other toys.
I think you should get one of the amp modeling boxes...you appear to be busy enough with outside stuff.