Don't Pee in the Pool
A rich man builds a pool containing only bottled water and invites a few friends over. He gathers everyone around and says, “Guys, I know it’s tempting and convenient to pee in the pool, but this pool is 100% Evian, let’s all try to use the bathroom next to the pool instead.” So everyone listens and enjoys a urine-free, delicious pool for the rest of the day. Until, of course, one of them breaks the rule, ruining it for everyone.
That pool is your commit history and the merge commits are the pee in the pool. So please, keep your pee out of the pool and rebase instead.
Disclaimer: I don’t really care if you do or do not pee in regular pools. This is all made up to illustrate a point.