Will it not kill bitcoin and make it useless?
Absolutely not, hoarders are what give bitcoin its value, bitcoin would have no value what so ever if everyone tried to give it away for other stuff. This concept is hard to understand at first but Holding savings in bitcoin is vital to the network. You should listen the youtube link i will post below, it explains it perfect.
https://youtu.be/e1eKHXdlx2Y?list=FL_1xDQgnywzy4JeHeRy1eKA
Roger ver pushes the whole bitcoin should be spent thing and then on the other hand admits that hodlers give bitcoin value