The effectiveness of a tire inflator is predicated on the driver catching the tire when the pressure first gets low. TPMS is a big help.
If the tire goes flat quickly, the inflator is useless because the structure of the tire is damaged by rolling on collapsed sidewalls.
So, the inflator won’t work if that damage is significant, the driver ignores the TPMS, or the car doesn’t have TPMS.
For those cases, the tire inflator is a lousy substitute for a proper spare.
My last real flat: a piece of debris on Route 13 on the Eastern Shore of Maryland Took our the right rear tire of my Volvo 240 wagon while I was towing a double axle Uhaul with a piano and furniture in it. The damage was severe, a several inch gash in the tread, and the deflation explosive.
I put the donut spare on the front right wheel. Moved the right front to the right rear. Drove to a tire store. Got two new tires.
No can of goop would’ve helped me. I would’ve been stuck, needing a tow, had to disconnect the trailer.
While I dislike donut spares, it was far, far better than a pressurized can of goop on that day. My cars all have full size spares (one actually has two spares, but that’s another story) and I won’t buy a car with just an inflator can.
There are some scenarios where the inflator is useless and you’re stuck, waiting for a tow. Given the time of day, and your location, that could be a very long, painful, wait.