It is a Rule of the Senate. Those rules are agreed upon by the members on how to proceed. Filibustering is a long tradition in the Senate, and it is seen as a way to enhance the ability to compromise and reach consensus.
The problems is that the Senate Rules have been adapted over the years so that a single Senator can put a hold on certain legislation and on certain appointments without even having to justify it. And out of it has also grown the cloture rule which requires a 60 vote approval to end debate.
But both parties are reluctant to change the rules because it might come back to haunt them if they lose power and the other party imposes the same changes on them.