Freezing/bouncing also lets you have more determinism.

Plugins with (often intentional) indeterminism in them, variations in OS and CPU architecture, variations in how fast their CPU is (a billion plugins on a track may run smoothly for one person and destroy someone else's machine), variations in sample rate, etc. can subtly or substantially affect how something sounds.

And in general it just makes things way easier to share even ignoring the issues of getting people to install the same plugin at the same version and the IP issues.