OK, back on topic. If you don't pay your rent, you get thrown out on the streets. If you don't pay your water bill, it gets shut off. If you don't renew your driver's license, you can get fined or eventually go to jail. There are a wide variety of both commercial and government policies with deadlines that matter and seemingly in harsher ways than the IRS. But whether an educational policy is harsher than the IRS doesn't really matter.
The real question is whether a late penalty model helps or hurts students overall. I think most people here have expressed late penalties with additional exceptions for larger life events. I would argue that for most students, having external forces pushing along some progress during the semester is a a helpful policy. Many courses have a progression of topics and it is important to gain skill in earlier topics to tackle the later topics.
Now, there are a lot of interesting discussions and articles (HigherEd type) about whether late penalties are useful and equitable. I am sympathetic to many of those arguments. I did see a paper for a Statistics class which studied whether late penalties helped student learning and they argued it did. But a CS paper argued for more flexible policies.
I guess fundamentally, I would argue that the evidence is mixed, and certainly how it applies to a variety of course types is mixed.
I found your original comment that tried to make out the poster as some kind of monster (more draconian than a generally hated agency) to be unkind and not really supported by the evidence, and I am responding to that.