This is a disturbing trend. Apparently a lot of these major streaming services are discovering that they can make more from ads than people paying for the service. At least when calculated with the subscriber counts they currently have. It seems they don't anticipate people leaving their services over this.
Personally there is no way I would ever pay for a service that has ads. I'm not going to pay for a service even if its paid service doesn't have ads if it has a free or cheaper service with ads as that would just be rewarding them for implementing ads.
For example with Amazon's plan here. If you pay this $3.00 to remove ads then you are paying Amazon $3.00 because they added ads. This only increases the amount of ads that will be added to things.
It's exactly this. Netflix makes more money from the average basic+ads user than they do from someone on the standard plan. It's incremental revenue from all users that even occasionally use the service, and invisible to those that pay for Prime but don't care about Prime Video.
If you pay directly for Prime Video only, it's a little different.