I have lifetime subs on a few MMOs. I don't feel the obligation to play them particularly, as I can log in whenever I want. However, if I've paid for a month of gaming, I'm more inclined to spend my spare time playing due to the restriction on access. For myself and perhaps others in the same situation, a lifetime sub is not much of an incentive to play. Sure, it's a financial bonus, but I like giving money to S-E so they can spend it on making/improving their games.

It's not so much about not wanting to try something new, more that S-E is high-calibre enough to attract players without needing to resort to offering a discount (and yes, the Legacy discount is appreciated, but I would have paid a regular subscription anyhow).