It's hard to charge for unchanging software.

Intuitively users feel that marginal price is fair if it scales roughly with the marginal cost to produce the marginal item.

Fixed cost one-size-fits-all-software has a marginal cost of effectively zero.

That makes that kind of software hard to charge for in the limit.

You can only charge for software that needs constant investment to keep it high-quality, or that gives access to an otherwise inaccessible ecosystem.

The ecosystem is separate from the software, but it keeps the overall value provided by the software fresh.