This works as long as there are only a few commits which don't build. It fails miserably if, say, 25% of all commits don't build (don't ask). In such a situation it becomes increasingly hard to tell what actually broke whatever functionality you're interested in: The commit you end up with or N prior commits which don't build (and which is incidentally usually full of "noise").

Why does it make it harder?

> The commit you end up with or N prior commits which don't build (and which is incidentally usually full of "noise").

The alternative, where things are squashed together, would leave you with just one commit but it'd be those N combined together (at least, it could well be more).

You can still diff between last good and first known bad. If necessary you can branch and squash the non builders to see what happened. At worst the intermediate commits gives you the same problem you would have if you had squashed to start with.

> At worst the intermediate commits gives you the same problem you would have if you had squashed to start with.

Well, if you're going to be bisecting a lot or compilation takes a while, it saves you time to do the squash now (when you know which commits are supposed to compile and which aren't) rather than when you come back to it.