I guess this is due to the supply and demand based on people's psychology?

Sellers want to earn more money, buyers want to spend less money.

Sellers want to sell their product with a high price. If they sell it once, they would give such a high price, that people wouldn't buy it, so they make it a subscription service.

But I assume, buyers of services assume that for services they get the benefit of a maintanance.

Just my 5 cents.