Many of them don't go into detail because 99% of customers don't give the slightest fuck. Show genuine interest, strike up conversation, and you can sometimes get a lot out of them.
In any case, service life in cars is usually determined by a couple key things: The design of the system, driving conditions, and service. You may feel like you're being blown off when the mechanic says "obey the service intervals and avoid short trips", but that's 99.9% of what you can do to make the car last.
(Special corner cases are widely-understood and well-documented, such as the impact of very high operating temperatures in automatic transmissions during towing)
In any case, service life in cars is usually determined by a couple key things: The design of the system, driving conditions, and service. You may feel like you're being blown off when the mechanic says "obey the service intervals and avoid short trips", but that's 99.9% of what you can do to make the car last.
(Special corner cases are widely-understood and well-documented, such as the impact of very high operating temperatures in automatic transmissions during towing)