Because a secret you should know about your ISPs is they really don't care (or want to care) about what you are doing with their service. They don't want to add the hardware/software it'd take to spy on your data, that's a huge cost to them with nothing but downsides.
I might distrust a large ISP more just because they have the extra cache to burn. But a smaller more regional ISP will not try and invade your privacy.
Because a secret you should know about your ISPs is they really don't care (or want to care) about what you are doing with their service. They don't want to add the hardware/software it'd take to spy on your data, that's a huge cost to them with nothing but downsides.
I might distrust a large ISP more just because they have the extra cache to burn. But a smaller more regional ISP will not try and invade your privacy.