Magento/Adobe is the automaker.
Agencies are dealerships.
Merchants are driving 10-year-old cars that just work.

The automaker wants to sell new car models. The dealerships want to sell you new models, as well. Dealerships don’t want to keep old tooling nor service knowledge.

Merchants like their 10 year old car: it makes money and works just fine. Trading to the new model costs more, has less performance, and they don't need all the new features.

The automaker says we're not making parts! But, aftermarket says we still have parts.

Automaker says but there might be a recall that we won't fix! Merchants say, “my car's been fine for 10 yrs I doubt there are defects. Plenty of mechanics still around to work on it.”

The new car model doesn't have the incentives to buy a new model. And to say that your old car is suddenly not safe after a certain date isn't true. Just because the warranty expires doesn’t suddenly mean you’ll be in an accident.