Hashing rate can be quite high if, for example, there is a China government funded attack or tens of millions devices botnet attack.
Also, calculated cracking time 50 years means that there is a 50% probability that it will be cracked in 50 years and 1% probability that it will be cracked in 1 year. I think for many people even 1% probability that it will be cracked in 50 years would be too high.