Stardock are actively trying to drive people to the subscription model.
You can buy a new "lifetime" Fences 5 license outright at the cost of 3 x the yearly subscription (not sure on the upgrade) but considering that version 4 is only 1.5 years old, they are trying to make the subscription the "value" item.
Considering that I originally purchased the lifetime license at less than the yearly subscription, upgrading is really poor value.
Lets also remember that windows 12 is likely here next year. Fences 6 could easily be released within 12 months.
Fences 3 lasted over 6 years before being superseded. I don't think we are getting that again.