so the engineers and designers throw it together in a way that makes for the quickest production to save time and money. They don't care about the next guy who has to work on it.
I'll bet there's more to this method than just madness. With the high % percentage of cars being leased for 4-5 years, I'm sure that some of these serviceability issues are deliberate and intended to make getting another new car much more desirable than keeping the five year old one. Probably why the 100000 mile service interval involves changing nearly everything.