Same reason all other libraries are not statically linked: Manly because that’ll break distro builds of Ardour.
There is a even a config option to do so, but it also results in a huge binary. Besides that’d be Ardour only, there may still be other hosts or other deployment systems (e.g. flatpak version of Ardour)…
PS. x42-plugins do statically link against libfreetype.
Another reason is that static linking is incredibly slow and while I care about users, I link Ardour dozens to hundreds of times per day. While in theory a simple switch for the release builds could work, that exposes us to another set of risks, since the version we’d be using day to day and for development would be linked entirely differently.
Just cloned & built ardour 9.7.276 from git, can confirm everything is working OK with LSP plugins 1.2.33.
Only problem i had was, i needed to remove my session load hook and restore it (scripting window) because it kept retriggering once at each second.