EEA still has the four freedoms which was not acceptable to the UK.

A smart person who has read up on EU/UK and some European migration situations will note that migration to e.g: Denmark/Switzerland is still difficult despite being part of those four freedoms. This is because they bothered to mitigate migration within the parameters of the law; since the right to work under EU's four freedoms only applies for 6 months.

But tariff free trade for goods benefits the EU more as the UK service sector is bigger than their goods sector. UK services companies (especially regulated services like finance, law, etc) are at a disadvantage to EU companies because the UK companies don't have equivalency (i.e. the either need extra checks (costs) to operate in the EU, or need to open a corporate office in the EU).

And, the UK recently decided to forgo their UKCA mark to replace the CE mark as it would cost UK businesses too much to support both.

And lastly the UK has yet to impose sanitary and phyto-sanitary rules on imports into the UK because it would cost consumers in the UK too much (UK food inflation is still higher than just about all EU countries even without the checks). But the EU does impose sanitary and phyto-sanitary checks on food imports to the EU from the UK. So, in net the EU benefits from this as well.

So in balance the UK doesn't benefit. And it's a huge deal.

I phrased my previous comment wrong (and should edit it). There’s of course a benefit to adopting the regulations and following the rules — you get to participate in the free trade area. But without a say in how those regulations and rules are formed.