I've had every butterfly key iteration from 2015 (12" MacBook of every iteration + 2017 and 2018 MacBook Pro 15" from work), and every single one of them needed at least one replacement.
I only have first hand experience, but no data to back this up, but I suspect that hard striking and a habit of striking off center could make it more likely you'll need a replacement. I intentionally struck my 2016 MBP as hard as I could for a month until one of the keys snapped off. The binding underneath cracked so it was no longer tethered to the butterfly. This caused a corner to sink in just a tad. The end result was that the key no longer activated unless you hit it right flush in the center or in the corner opposite of the break.
This is a keycap misalignment. This will cause an unresponsive behavior and possibly also a repeat if you hit it just right. In my case it was easily fixed. I took the broken keycap and turned it upside down so that the broken corner was on the bottom instead of the top.
Flipping it 180 degrees worked because the butterfly mechanism is actually not a switch. It's a stabilizer. I tended to hit the top edge so when the fracture was near the area of the key that I struck the most, it resulted in the butterfly not collapsing.
The butterfly and scissor mechanisms are what allow you to strike the corner edge of a key and have the entire key come down as if you struck it dead in the center. Otherwise a glancing blow will wobble and not trigger the keypress.
The type of switch in both scissor and butterfly keyboards is actually the same. They both use rubber membrane dome boards. The scissor and butterfly stabilizers just affect how the force of your (attempted) keypress gets transferred to the dome switch.
The mechanism of the scissor stabilizers are flexible so if something goes wrong, the switch can still come down, but with wobble. The butterfly mechanism is VERY HARD. It doesn't wobble an iota. That's how it can get stuck.
Because the butterfly mechanism is so hard and has so little clearance room, hard debris wedged into just the right spot can cause it to jam, but this really isn't that easy to accomplish. You need more than dust as is commonly believed. Also because the butterflies are so hard, anything that is semi-solid will get crushed. It can cause some temporary issues, but will probably go away after a few days of regular use.
So for the keys to get stuck you'd have to somehow manage to get teeny pebbles under the keycap or something will have to cause either the keycaps or butterflies to misalign. Very hard off-center striking could accomplish this by fracturing the underside of the keycap. Some people believe heat is the big culprit and I could see that as a factor. If heat caused some of the butterflies to warp just a tiny bit, it could cause them to no longer collapse cleanly.
I have a 2018 MBP now. No keyboard issues at all in the 6 months I've had it. My 2016 also only had it for the first year of ownership. It actually got better the more I used it. Some of them might actually get better with breaking in as my old machine did.
A piece of dust getting under a key is enough to destroy an entire keyboard. That's not user error. That's the result of piss poor design.
Dust alone won't do it. iFixit found that a grain of hard debris could jam it. What got erroneously repeated was that an ordinary speck of dust could break it and that's what everyone's been repeating ad nauseum ever since. If you study the mechanism of how the switch and other keyboard switches work, it'll make a lot of sense. You'll need a lot of dust before can impede the butterfly mechanism.
This would explain why compressed air works for some, but doesn't work for others.
I'd be willing to bet that the compressed air really worked for only a very small percentage of people and for others it was just a placebo because based on what I've figured out of how they can jam, some of them would have unjammed with some repeated presses. I cleared my jams just by pressing down hard and jiggling it until they stopped happening. Stuck keys caused by misalignments of the keycaps could even improve just by turning the laptop upside down.
Why would they suggest compressed air? Beats me. My guess would be that it was better than telling people that there wasn't really anything they could do about it and also compressed air was already known as a keyboard fix for mechanical keyboards. Mechanical keyboards are susceptible to dust because dust getting into the switch itself actually gets onto the electrical contacts. Compressed air blown directly into the switch can sometimes clean them enough to stop the key chatter.
That's not possible on a butterfly keyboard though. The butterfly keyboards switches are not exposed. They're sealed rubber domes. You're not getting dust in there unless you're sandblasting your keyboard.
