@Jennifer ********
Sadly, it is their business. They want to know where all foreigners are staying at at all times, so they made the Immigration act. If you have an apartment that you're renting, and you stay at a hotel room, the hotel will register you in immigration's database. Once you leave the hotel, you'll have to let your apartment owner know you returned so s/he can immigration know.
I live with my wife on our land. My wife HATES having me to go down to immigration to submit the TM30 whenever I come back from Bangkok, but that's what the law says, and that's what I do. Thankfully, it's a quick 2 minute process for us, but it might be longer for other people.
It's their rules, their laws, and we have to obey it. We have no right to be in Thailand