Maybe, just maybe because that spam is not the bussiness model of your email provider.

Yes. They are not biased by a conflict of interest so they can offer users exactly what they want.

Offering everything users want only can be done when they are paying, otherwise they must accept the little things they don't like such as the main income source of all the websites they like to use. It would be like google asking all other ISPs to block this French ISP just because they don't like their business decisions.