I'm trying to understand what reasons the law was written to expressly exclude sales by certain relatives (linearly)? What is the motivation for excluding?

I have home shopped & it makes the most sense for me to buy where I've been living for a number of years which is owned by my parents - at market value. For a few reasons including disablity it's been hard to locate something else, & the local market has an inventory shortage. Plus, costs have gone up & my parents would have to raise the rent to more than I'd pay for a mortgage. I had tried shopping & buying a couple years ago but prices were too high & this crash is the perfect time to buy. It was an investment property for them & they owned several for a long while as their business.

Does anyone have insight? Thanks!!