Why do so many German students of English say /pʊə/ for <poor> and not /pɔː/?
According to the LPD almost 80% of the younger generation of General British speakers use the latter variant, but more than 90% of my German students use the former one. Probably, one of the reasons is that they were taught English by teachers whose English-speech-forming years were the 50ies and 60ies of the last century when the diphthongal pronunciation was much more rampant than it is nowadays.
Should students worry? Actually not if they prefer to belong to the minority of native speakers of General British. If, however, they want to sound young and fresh they may want to switch to the monophthongal version.
BTW: If you're shore you saw the Shore on the shore, rest ashored that yore impression was caused by yore paw vision. (Can you spot the intrusive r-sound in the previous sentence?)