Hobo said:
No it doesn't, and no there isn't.
Although I will agree that the baseless fear of those mysterious "cascading changes" seemed to have discouraged a lot of folks from houseruling.
Never discouraged me. I played very heavily houseruled 3e variants pretty much right from the get-go. Never had a single problem with "cascading problems" or the so-called "tight integration" of the rules.
Indeed. If anything, having a (somewhat) 'more universal'

resolution system makes it easier to see what flow-on effects there might be, or might not be. IMO, that is.
When you're dealing with lots of little subsystems,
there are still going to be flow-on effects from time to time (and yes, just as many) - but often, they won't be as obvious to the observer. That's the difference.
That said, I'm not opposed to using a boatload of subsystems in any given RPG. Both ways are fine by me, and I will probably end up house-ruling either one anyway.
What 'makes' us house rule? One size does not fit all. Your campaign - or hell, your character concept - isn't necessarily going to mesh perfectly with the ideas, methods, reasoning, beliefs and so on, of some random designer(s) out there. Or hey, you might pick up things about the mechanics in general, that you can improve, sometimes subjectively, other times not so much.

Simple as that.
As for different systems being easier to house rule (i.e., lending themselves to it,) I guess I've already made on epoint there. Otherwise, of course, the more complex the system, the harder house ruling is. Can't think of any other major factors, quite honestly.