I think it is related to competition. Lack of competition brings complacency of executives, who think they can get free money for shareholders without having to reinvest into innovation. (And I think that was carlmr's point.)

Of course, if you are bigger, the more likely it is that there is no competition at certain times.

Yeah, my point was that a big company can coast without innovating. They usually have a lot of stuff to sell that they have done in the past. The pressure to rejuvenate comes from outside, rarely from the inside (surely there are exceptions as with every good rule).

If you can survive without investing, a lot of companies choose not to.