1. They allow easy access to upgrades, and make it far easier to make sure everyone is on the latest and greatest (you aren't paying for every upgrade, so there is little incentive to hold out.)

2. The consumer pays far less up front -- for example, Adobe Creative Suite costs $600+ and that is money you have to pay upfront. Or I can pay $30 a month to use all of the software in that suite. In my example, I would never buy Photoshop as I can't justify $600+ in price for my uses. $30 a month I can justify. Basically, as a consumer I get access to software/functionality that I never would have had access to before.

3. I only pay for as long as I need it. If after a 6 monhts, I no longer have a need for the software, I cancel my subscription. As simple as that. I have not wasted a lot of money.

4. Which leads to making the software publishers work harder to put in features that help a larger base of users, not just corporate users. And to provide theses features on a more regular basis to keep me paying the monthly fee.

Sure, you can look at it the way you are suggesting but overall I think it is a win/win scenario.