Earlier quoted context omitted.
Note that those aren't "change commits", but merge commits aggregating large swathes of other changes. And it's not even all merge commits, it's just the merges from Linus' "top lieutenants". But I sympathize. I often spend more time on commit messages than the actual changes...
Writing long commit messages (especially for internal/private projects) often gives me a slightly forlorn feeling, knowing that these words will almost certainly never be read again by another person, and possibly even I might never see them again. I persist only because when they do get read, they can be absolutely invaluable in explaining what on earth I was thinking at the time.
I really am thankful that you do write long commit messages. As a student starting out in OSS, I have had to track down why the particular piece of code is written like it and I go hunting down git blame and that really helps me. I also follow the practice when I can and hope that it helps future contributors or maintainers.