If the SaaS has ongoing value -- for example, if it involves a hosted element that uses resources each month -- then it can be worth ongoing payments. Its value to the customer increases over time.
If the SaaS is just a static piece of software -- or something that might later receive updates of unknown value that you might or might not actually want anyway -- and it's something you will need for the long term, then it probably needs to be much cheaper to rent it than to buy it outright before it's economically worthwhile. Its value doesn't increase over time, so you have to compare the expected cost for as long as you think you'll need to rent it with the one-time cost of buying outright. Even then, you still have the security of your investment to consider if there is no guarantee that the software will still be there or still work the same way when you need it later.
In other words, yes, a lot of SaaS is also greedy.
If the SaaS has ongoing value -- for example, if it involves a hosted element that uses resources each month -- then it can be worth ongoing payments. Its value to the customer increases over time.
If the SaaS is just a static piece of software -- or something that might later receive updates of unknown value that you might or might not actually want anyway -- and it's something you will need for the long term, then it probably needs to be much cheaper to rent it than to buy it outright before it's economically worthwhile. Its value doesn't increase over time, so you have to compare the expected cost for as long as you think you'll need to rent it with the one-time cost of buying outright. Even then, you still have the security of your investment to consider if there is no guarantee that the software will still be there or still work the same way when you need it later.
In other words, yes, a lot of SaaS is also greedy.