It's been a traditional courtsey in the Senate for the party in power not to shove through votes often, in respect that in the future they would eventually be the minority party, and occasionally need to filibuster as well. The possibility of removing the ability to filibuster has been discussed, but not undertaken for this reason.

By filibustering so often, the Republicans are showing that this is no longer the custom. Which is fine; I think it's a silly custom, and we'd benefit as a nation if blocking legislation like that were impossible. But it is absolutely a break from common procedure.