Getting a big seed round once makes you want that next round to keep going (and take even more money off the table).

Getting a X-million-per-year budget from a parent company gives you a very different sort of situation. IME this results in less urge to get something out the door and more urge to get "the best thing" built. Shipping early risks your budget in a way that "look at all this cool theoretical progress" doesn't, because the public and press can critique you more directly.

Lack of major owner equity basically means few intrapreneur efforts will succeed unless the 'founder' really couldn't succeed without the daddy company