I think tandemming just places heavier strains on the tyres. You're braking and accelerating with greater force, all of which has to be carried by the sidewall threads.
We (two heavy guys) destroyed a Continental Top Tourer on a hilly ride preparing for an E2E, catching a nastily bulging sidewall just before the tube went bang. Replacing front and back, again with Contis that had come as spares with the second-hand tandem, they lasted fine---not a single puncture in 1100 loaded miles.