If something is hard, that's an argument for making a standard not for profit version of it, so it becomes a common good instead of platform rent seekers keeping out competition by saying it's "too hard".
Like a slumlord who collects rent and does nothing to even maintain the property. Except perhaps vote down YIMBY reforms.
Rent seeking would be designing a product for collecting rent (not a one time payment) for a product (e.g. SaS) that doesn't wear out or has separate maintenance costs. Like a house that is rented the value comes from the income stream and it likely is adjusted by something like inflation.
Not renting would be selling a product for a one time fee, perhaps even if there are many customers (you still get to play ticket pricing games like the airlines so different people pay different amounts at different times, but not as variable as rent). Making the product non-transferable blurs the rent line a bit. Also not rental is the maintenance or improvement on the product (or the house) since that is new work that is being done.
It used to be that only physical objects were rented and services were inherently work and required new effort/ingenuity to be solved each time. However, with the introduction of art reproduction (visual, audio, physical) and copyright/patent, as well as, non-perpetual licensing of software this is no longer the case. It's possible to hold a piece of intellectual property and collect perpetual rent with little or no future investment.
It does create a different incentive structure that can be quite customer hostile.
It's not just general and optional recurring payments.
- actual rent-seeking (as you say, not really true for companies such as Microsoft and Google, except where you see e.g. government documents needing to be submitted in Word. But that's very likely incompetence on behalf of the bureaucracy rather than Microsoft)
- having a dominant market position due to having a very high quality product, or set of products that work together well
- a random grudge phrased as rent-seeking, because the Twitter user in question doesn't know what rent-seeking is, but has seen their friends accuse companies of it
I don't know what the proportions are, but I suspect the former is minimal to nonexistent for e.g. Google.