Because tax freedom in
Thailand doesn't require spending half a million dollars. You can get the same result with cheap $1k/year visas, or, if you want to get fancy, a Thai Elite visa at $40k for 10 years.
There is also a $300k investor visa that has no time limit and can be renewed annually forever (decades ago it was a $100k
investment, and people from those old visas were grandfathered in and still renew it showing their $100k investment).
In other words, the LTR visa by investment is the worst deal of all of them, by far.
Thai Elite is the easiest of all. The 90-day reports literally take 1 minute nowadays. You can also do them online, or have an agent do them for you.
Buying and managing your own $500k property is not necessarily an stress-free experience. Also, remember that remitting the $500k to buy it would also trigger a tax event if you don't plan accordingly... So you won't be free of planning, even if you decide to overpay.