They probably showed up at the airport with bags and carry-on stuff, not knowing that Spirit is rather different and charges for everything beyond getting you there in what some friends described as the most uncomfortable seats in the skies. Select a seat? That’ll cost ya. The checked bag? Another charge. The carry-on bag? Yep, they’ll charge for that.
The last time I went to Chicago, we each had two 49-pound checked bags, a carry-on, and a “personal item” On a round trip, that would cost about $270 each beyond the cost of the flight if we paid at the time of booking. If we showed up at the airport without pre-paying for bags, it would be nearly $360 each. (probably could have flown on Southwest for $400 each with no surprise bag fees) And another $24-500 each (no idea why such a huge variability) if we wanted the “Big Front Seat” which is more or less a first class seat but they’ll still charge for bags.
Air travel is so safe nowadays trying to categorize planes or airlines as safe vs. unsafe is really splitting hairs. They’re all safe, assuming you’re not looking at dodgy fly by night airlines in developing countries.
Yes, I suspect a lot of people just see the low fare on Kayak or wherever, and book a flight on Spirit without doing any research as to what they’re getting, and more importantly not getting for that low fare. And they just assume they’ll get all the same amenities “every” airline provides, and are shocked when they find out they’ll have to pay for even their larger carry-on bags (IIRC Spirit charges for anything that doesn’t fit under the seat), and for beverages, and all the other things you mentioned.
I’ve never flown on Spirit; they didn’t serve my home airport until fairly recently. And I’m not likely to just because I’d prefer a few more amenities than what they offer (at minimum the ability to pre-select my seat, a free carry-on, and a beverage). But if you can pack light, and don’t care where you sit, and generally know what to expect, Spirit can be a cheap way to travel.
And the dentist will give you a local anesthetic. (I suppose the airlines do also, if you consider alcohol an anesthetic, but the airlines will cut you off when it gets to the “feeling no pain” point.)
Sedation offered at the gate (for twice what you’d pay anywhere else) is the coming thing in air travel. Patients I mean clients will then be layered on shelves for transport.