Many reasons.
For one thing, the game is sentimental to me. My grandfather bought me my first computer and The Sims 1 for my birthday as a kid. He was super excited about it because the lady at the store told him that the game was a “dollhouse simulator”, and I had addictivly played with barbies since I was a toddler and was arriving at the age that I was starting to outgrown playing with them. I loved the game immediately, and when he would visit we would play together; him guiding me to build and decorate different houses and reminding me to keep an eye on the sim’s needs. He passed away several years ago, but I think of him every time I play. Especially now because I think he would be so amazed with all the cool stuff you can do in the game these days.
I also play as a creative outlet. I love decorating houses and working on my building skills. I love telling stories with my sims. It also really helps me relax and unwind.