Why do steaming services think they have a captive audience and I'm not going to ditch all of them with the crazy influx of annoying ads?

Streaming services have a catastrophic problem they didn't see coming.

As they massively expanded the viewing market, they also gave very accurate viewing metrics compared to broadcast TV.

Also, the many, MANY offerings cut the viewing pie into smaller pieces.

And this is the expectation, mostly because while you might stay with a super hit like GoT, they're super expensive, and huge risks if they don't take off (see acolyte). Cost sensitive people are likely to subscribe for the season then cancel, or just subscribe the month the season finishes.

The alternative is to try to hook you on a bunch of shows, which means having a ton of them and hoping they nail your niche. People are less willing to do this, but it works if you have more disposable income, or value streaming more.

In any case, they can't afford all the shows they have to put on, it's all or nothing now, before they might watch lost on ABC one night, then CBS walker Texas ranger might let the kid fall on the ground the next, but now you have to keep them entertained most days, that's a shit-ton of content. HBO has it worse, they're losing their old cable revenue, and their productions are stupid expensive, and they're one of the winners. Disney has it even worse because disney+ cannibalizes both their cinema sales and they have to put up their crown jewels, star wars and the mcu, all on the same service, devaluing both. Fortunately focusing on kids programming helps because parents basically have to have Disney+ just as a matter of course.

This barely worked on broadcast because the different channels could share the load and cut the ad pie into larger pieces,

If they could count on must-watch blockbusters (ie GoT, which really hurt them when they screwed the landing and killed rewatchability), they could pull it off, but that's so risky, it's betting everything on one spin of the roulette wheel.