CLAP might be similar to AU in plugin support which is pretty common too.

CLAP is nowhere near close to AU in adoption.

Almost all VST plugins have an AU version (like 80%-90% or so, and 99% of the major ones).

Almost no VST plugins have a CLAP version (like 1%-5%, and that's charitable).

I know it isn't nowhere near in adoption NOW. I meant it shows there is room for another format and AU is a good example of how another format can make inroads.

AU support grew because Logic Pro only loads AU, Logic userbase is a attractive enough market for plugin devs.

On the other hand, there is not a single DAW that only loads CLAP.

That's the same problem Steinberg faced with VST3 years ago, every host/DAW/plugin supported VST2 (including Cubase), there was no reason for devs to switch to VST3.

Steinberg forced the issue killing the VST2 licenses, any new plugin and host had only access to the VST3 license, even then devs resisted, only recently Steinberg announced future Cubase/Nuendo versions won't support VST2 anymore (plugin devs may hate Steinberg, but they won't simply leave Cubase/Nuendo users without support, they are not to blame for Steinberg's stupidity).

CLAP can't force the issue the same way Steinberg did with VST3, there is no CLAP-only DAW either.