which is completely logical, because the hotel or other adress you visited should also do TM30, so how should immigration know you returned to a previous address.
tourists planning long trips to a number of countries prepare the necessary visa in their home country before they travel. People who stay already in Thailand and need extra time are not tourists. And of course the fact a lot of people profit from this bypassing the system might keep it alive.
I think Thailand has visa for almost every purpose, so everybody who is not a dummy can just apply for a visa. Staying for a long time in most other countries also needs to apply visa, so why should Thailand be different?
there is no 2 exempt land crossing rule. Of course they can make rules different, but stricter rules means real tourist get inconvenience, because there is a hardcore group trying to live in Thailand, refusing to buy a visa for their purpose. And don't forget, for long term tourists METV exists, but of course you can try to profit from free entries as long as it gets, but the visa exempt just is tot created for that purpose, and by using it, you accept that you depend from the individual officer.