Others have pointed out the specifics related to websites and GDPR/the ePrivacy directive, but there's another example of why what you say isn't really true that might help understand, and that's EU (and for now UK) consumer law.
A site might have terms and conditions, or conditions of sale etc. but if you as an individual buy something you still have protection from consumer laws. Any conditions you agree to are only ever in addition to your statutory rights.
So, a company might state that an item has a 12 month warranty (as happened with me, a Mac computer bought from Apple), and it might break after that time (mine after something like 13 months). In my case Apple said they were not going to fix it for free because it was out of warranty and I didn't have Apple care (deliberately because I knew consumer law), but I successfully argued that (as stated in the legislation) that there was a reasonable expectation that the item should have worked for a lot longer than that, ultimately making them responsible. They did in the end accept this and fix it.
There's other examples, like if an item is not as described then the company selling it has to pay costs to have it returned, and that the company is responsible for the item while it is in transit in either direction. You are due a refund within 14 days of the /rejection/ of the item, not any other timescale, or dependent on when you return the item, etc. etc.
In summary, your "terms and conditions" are effectively irrelevant if they attempt to reduce or bypass existing legislation.
A site might have terms and conditions, or conditions of sale etc. but if you as an individual buy something you still have protection from consumer laws. Any conditions you agree to are only ever in addition to your statutory rights.
So, a company might state that an item has a 12 month warranty (as happened with me, a Mac computer bought from Apple), and it might break after that time (mine after something like 13 months). In my case Apple said they were not going to fix it for free because it was out of warranty and I didn't have Apple care (deliberately because I knew consumer law), but I successfully argued that (as stated in the legislation) that there was a reasonable expectation that the item should have worked for a lot longer than that, ultimately making them responsible. They did in the end accept this and fix it.
There's other examples, like if an item is not as described then the company selling it has to pay costs to have it returned, and that the company is responsible for the item while it is in transit in either direction. You are due a refund within 14 days of the /rejection/ of the item, not any other timescale, or dependent on when you return the item, etc. etc.
In summary, your "terms and conditions" are effectively irrelevant if they attempt to reduce or bypass existing legislation.