Main points are:

1) Most people will come into cryptocurrency through Bitcoin

2) Bitcoin has "good enough" privacy in some cases, and can be drastically improved still

3) Bitcoin's network effect mean that my work on Bitcoin can have an outsized impact compared to Monero

4) Monero doesn't need what I can do as much anymore, lots of other's have taken up the mantle

5) If no one sticks around in Bitcoin to push for non-custodial/private usage, that will die and Bitcoin will be a Panopticonic nightmare for the world, so I can keep doing my part to push against the tide of "adoption", KYC, and custodial wallets etc.

6) Lightning shows a lot of promise of non-custodial usage + privacy improves, all of which is possible and most needed solutions have already been proposed