A ton of patented stuff is regularly reinvented by people. In many fields, key ideas are so well-understood by practitioners that who patents them first is mostly a game of chance.
There's no point to allow someone (usually a company that does nothing but sits on patents) to do nothing while blocking everyone else from independently reinventing and implementing it. It is especially spearheaded against companies which buy and then bury an idea to preserve their incumbent status for 25 years more.
A monopoly is a bad thing. Sometimes it's a lesser evil, but most often it's not.
However, I think the balance generally works in the other direction. 20 years feels excessive, but it’s arguably fast enough that taking something from a lab to mass production often eats up 1/2 the time. Further, many patents that are obvious like asteroid mining are going to expire long before their practical. On the other hand simply waiting out the clock to manufacture something means being really behind, thus pushing licensing.
That's only true for the public.
A company may not with to license patent use under truly fair conditions, because it would compete with their products using a different technology, they may not with to license to potential competitors, and/or small businesses (fairly).
Alternatively, holder may be using the patent, but choose that their current cash-cow is good-enough so why support competition and innovation, when they can just bump it up slightly every 10 years or so.
Defensive and overly broad patents are definitely a thing, but the intent is to give a monopoly for a limited time. Locking down alternatives not currently in production that are obvious workarounds is kind of a requirement for most patents to be meaningful. The issue is when a company in effect owns an industry and then keeps submitting obvious patents. But, here the problem is with obvious patents being granted.
Wasn't the original purpose of patents not to protect big business's hockey-stick grown, but to allow small inventors to capitalize on their inventions (and not have them shamelessly ripped off by some big business). I think the other original purpose was to make sure inventions would eventually become publicized and exploitable by all.
That exponential patents idea seems like it would render patent protection prohibitively expensive for all except maybe the rich or inventors unusually well-position to quickly capitalize on their invention. The little guy who takes ten years to get his business off the ground is out of luck.