Which is a consequence of BSD style licenses, yet every time a project switches from GPL to something in the BSD spirit there are jumps of joy.
So in the long run it is back to the old freeware days, with the lower lever free and everything on top closed, with zero contributions.
That didn't seem to work the same way for say.. mail server software?
Sendmail, postfix and qmail all had BSD-ish licenses, and those three covered quite a majority of all opensource mail serving at the time of BSD-vs-Linux "in the same early years"
PostgreSQL, LLVM, Apache, Nginx, Xorg - all of those are covered by liberal licenses, not copyleft ones.
Drivers for hardware that is better supported in Linux compared to FreeBSD - 90% of which is graphics - are usually licensed as MIT or BSD, not GPL, even though they are shipped as part of the Linux kernel.
So, nah, it's not the license.
The Linux users gave back (often because they had to) and the BSD users often didn't.