Actually , the tape transports ( especially those in cars which are subjected to more abuse  (heat, cold ,humidity ) will cause more problems than the tape itself.

Capstans and pinch rollers, which are generally quite inaccessable for a good cleaning,without disassembling the machines , will collect all forms of oxides, causing a chemical soup to build up on their surfaces. 

Next, the  belts and clutches used in the spindle drive mechanisms will eventually fail, again due to heat, cold, and use , and when the takeup spindle no longer has sufficient torque to pull the tape away from the pinch roller and capstan , the oxide soup will grab the tape, wrapping it around the capstan or pinch roller.

Not to mention the disintegration of greases and oils used to lubricate many moving parts,which when they do,leave behind a gummy residue which makes operation all the more difficult -especially for small drive belts

Of course all of these things also can occur in an indoor based unit, but many of the problems that can occur in an indoor based unit happen much more quickly in a car simply due to their operating environment. 

I have known some users- even those who ought to know better- who will immediately thrust a cassette in their car machine -in the dead of winter - and curse a blue streak when the machines' stiff as a board transport destroys their tape. 

Rubber parts and drive clutches simply don't work well at 20 degrees farrenheit.

Never have - Never will    ( IMHO)

> Cassettes are actually, for the most part, proving to be reasonably
robust. I
> just transferred some early-'70s cassettes and the biggest headache with
> non-major-brand ones were that the splices failed.
In fact, I found...and still play occasionally, half-a-dozen or so Philips
cassettes, recorded by me back in 1968 when only Philips made
they still play as well as they ever did. I also have about 200 cassettes I
made between 1979 and 1983...mostly name-brand but with quite a few "no
as well...and they also play as well as they ever did. My player is
a Sony portable "boom box," itself probably c. 1990.

The main problem I've had with cassettes has been the players...usually ones
vehicles...which occasionally "eat" the tape, which then has to be carefully
rewound back into the cassette. I suspect this is caused by contamination in
the players, not on the tape.
Steven C. Barr