Agree. However the core problem with most SAAS products is: the companies are beeing greedy and the products fail to deliver enough value or keeep missing a certain quality bar to make you happy.
You could easily fix that by a base price and a maintenence fee (per year, since first buy) which would make it easy to opt in/out of a subscription model. The fact that companies are beeing greedy and fail to deliver prevents this from happening.