Your ISP does not have access to most of your communication, social media usage and searches as that runs thru https.
That is why Facebook and others is completely blocked in China. Had the national carriers been able to surveil and block select communication they would have been asked to do so by the government.
Secondly an ISP charges you a subscription and that is their revenue model. They are not incentivised to build an elaborate profile on your in order to deliver advertisement.
Thirdly ISPs in most countries are required by law to support the police with surveillance information. That is done in transparent way (you can read the laws and ask your politicians).
This police support has always existed sinces the days of the tele monopolies. However now that more communication runs via internet, https and social media, it creates this strange inbalance where the police cannnot get the same access to Facebook (or similar) communication as they can to SMS or voice communication.
Also Facebook provides different level of access to the NSA, the police in Denmark and the police in Myanmar. And do that in a non-transparent manner.