If you think about it, it's not weird. In the UK (and if you are a certain age), you weigh things in pounds and you buy things in pounds.
As I see it, it's the same principal as Baht. Someone will probably correct me
Buying gold from a reputable shop is generally seen as an insurance for Thai people. When they have some money, they will buy gold and when their luck is down, they will sell often at a profit providing the price go's up.