I would disagree with the assertion or assumption in the question that TR's as "so faulty" and significantly less reliable than other systems. Based on my experience, the reliability of TR's is probably between 99% and 99.9% -- in other words the times when a TR fails to work is between 1 in 100 and 1 in 1000 flights. That, to me, doesn't look like a particularly bad record.
Modern aircraft in general are extremely reliable, so when you compare a component with a 99.x% record against a component with a 99.999% record (say, a windshield -- how often do you see those fail?), the former doesn't look good in the comparison. But when you consider that there are thousands of commercial flights daily in the US, and it's uncommon for anything significant to make the news, the reliability rate for the system as a whole is extremely good.
Some of this is fault tolerance; on most runways, unexpected loss of a TR doesn't affect things very much. The vast majority of the time, braking performance is entirely adequate to stop the aircraft well before the end of the runway even with no reverse thrust (not merely one of two or one of four failed).
But in over a decade of flying modern jet aircraft, the number of times I've seen a TR fail to deploy I could probably count on the fingers of one hand, so all in all I'd suggest that they tend to be quite reliable.