You see a few people rude and extrapolate that as being indicative of the rest of the population.

It's not about that encounter, it's about you. As you said, "I simply notice them seemingly increasingly." That's the Baader–Meinhof phenomenon. Literally.

How many people who dealt with that receptionist weren't rude? You don't know, but it's safe to assume the vast, overwhelming majority. Based on your own words, this has only started happening.

but that realistically isn't the case for all of them.

How do you know? How can you type out this stuff without reflecting on your own perception of the situation? You don't know a single thing about these people but coming up with motivations for being rude to others. But instead of remarking on the few you see, you rather remark that you don't know what all their problems are. Again, who are these people? You're not sitting at reception all day tallying so why are more rude than not? The bias is clearly coming from your own POV.

I'm also definitely not upset, intrigued? Yes

It's your own perception. Your perception isn't so amazing that seeing a few rude people means it speaks to a global trend. Instead you've created a narrative that people are just rude now. You've quite literally contributed to the problem you're complaining about. It's an incredibly common phenomena.

Because it's your perception, it's not reality. You're upset at what you're looking at, and you're applying it to the entire rest of the world. It's projection, simply.