So many online services, so much legal information, usually written in confusing ways.

For example, in data processing addendum, Porkbun uses the term "Controller", which is defined as:

(d) “Controller” as used in this DPA, means Customer.

Why not just call it Customer?

Worse yet, just like many services, Purelymail has this in their ToS:

The Company reserves the right to change this agreement at any time. You are responsible for regularly reviewing these Terms. Continued use of the Service after such changes shall constitute your consent to them.

In this case, there isn't even a date of last update. Am I supposed to have some scripts scraping all legal documents of most services every hour and comparing checksums to figure out if something has changed?

But how should I even keep track of legal agreements of many many companies including any affiliated third parties I implicitly agree to use?

Because it sounds like I should also be concerned about those:

Sub-processors authorised under Section 7 of the DPA process the personal data described above for the purposes listed above and only for the duration necessary to perform the sub-processed activity.

If I was to read, understand, and keep track of everything, I feel that would in fact just become my full-time job. Especially since they often also reference laws, something I would also need to know and understand.

Subject to applicable law [...]

Which is what?