That's the rationale Linux people give. But FreeBSD has managed to maintain much stronger backwards compatibility (with older ABIs gradually moved into -compat modules and eventually removed entirely) than Linux without it noticeably damaging kernel development speed. Linux is the only major platform where hardware that worked frequently stops working (not just because of closed-source drivers; the same problems exist for open-source drivers that are out-of-tree for whatever reason - there are plenty of high-quality open-source drivers that the kernel doesn't accept in-tree or that don't want to be in-tree), and what do you actually gain for that high price?