There are only a handful of demos that require anything beyond a base C64.
That is why I love the C64 scene so much, you can just buy yourself a cheap C64 + drive and run 99.9% of the software base.
With Amiga, unless you're only interested in 80's software, you must expand the system.
I had to buy an 060 accelerator to enjoy Amiga demos from the past 10 or so years, that's quite an investment just to run demos, but I don't regret it for a second
Also, these days all the big quality productions are released only in parties, unlike the old days, so release frequency depends on the number of parties...
Its something we have to live with I guess.