Not at all
Has been done for years, is currently done now will continue to be done.
Look here is the reality
Software is not static, it requires maintenance, that is ongoing development, support, etc so there is a cost to keep it viable over time.
Okay, this means the users that use it, well they have to account for that cost over time in some way. You can either inflate the buy-in price but let me assure you that you will never buy software again 
If you average out the cost of supporting and developing an asset its … well lets just say its not cheap
The reason for this is while you might ask 1 or 2 questions here and there … there are much larger clients that take hundreds or thousands of hours of support and need updates and changes in a quick turn around
Hummm … okay well bill them differently… ah yes and use the honour system to right?
So your really going to rebuy all your tools at the 10-100x markup that would be required for the commercial version?
No I didn’t think so
Okay so what if we simply billed you for what you used … this would be fair
If you have zero need for any updates or support, you just pay once and that’s it all done
But if you are a bigger client and you need support and updates … well you pay for that of course
Okay and what do we call that?
O wait … we call that a subscription
You subscribe to the service you want to get
Sure some stores and products call it a “Yearly Release” … or “Maintenance” or “SLA (service level agreement)” or whatever
but lets be plane about it
Its a service you are subscribing to for some period of time e.g. it is a subscription by any other name … its just a subscription
Will some products try and find ways to force you into the sub … yep
That is called SaaS (Software as a Service) it has its use cases, not have many, but it does have a few use cases. Live games for example MMOs, MOBA, etc. they are services not products. They are not permanent sorry, and while some try to hide the “subscription” fee behind season passes, expansions, etc. the reality is there is an ongoing cost and if that isn’t accounted for they go away
In the realm of tools and assets, there are services, PlayFab, GameLift, etc. again they come with a bill, dont pay, dont play.
For what I am talking about though, tools, integrations, frameworks … these are products. So they should have a perpetual license. The updates to them and the support for them … that is a service and yes means you need a subscription … no matter what you want to call it … it is you as a user subscribing to those services (updates, support, etc.)