Ok so Cato "filibustered" on two occasions. The first was in 60, when Caesar was awaiting his Spanish triumph as propraetor. Caesar requested that the senate accept his candidacy for the consulship in absentia, as the date of the consular elections was fast approaching and he had not yet been able to enter the city. Cato opposed the motion (on what grounds it's hard to tell--Plutarch says ἰσχυριζομένου τῷ νόμῳ, "maintaining the law," which doesn't make sense since it doesn't appear that legally a candidate had to submit his professio in person before 52, and there were precedents for candidates who did not) and ran out the day for the discussion--the senate could not convene after sunset legally. The second was in 59 when Caesar as consul asked Cato's sententia on the agrarian bill--Cato attempted to delay proceedings in the senate for the whole day again, and was promptly marched off to jail.

What's notable about both these instances is their setting, and thus the strict legal nature of the discussion that was stopped. Both filibusters were delivered in the senate (Plutarch erroneously believes that the filibuster of 59 was delivered before the people on the rostra, which is impossible and contradicted by both Suetonius and Gellius). The deal here is that the senate's vote was not law. Senatorial meetings resulted in the compilation of all the sententiae (the opinions given on the matter by senatorial speeches), which were then voted on by the senators. The result of the vote was written down as a consultum, a resolution that was issued to the magistrates--generally bills destined for the citizen assemblies were first referred to the senate, and if the vote there failed usually (though not always) the magistrate proposing them did not bring them to an assembly vote. This was as far as the senate could legally go in most cases (except in some, e.g. the appointment of extraordinary magistrates), and the consultum was only technically advice, it was not legally binding, though the consequences on one's career of ignoring it could be dire. So in the case of Cato's second filibuster Caesar went ahead and brought the bill to the citizen assemblies for a vote anyway, where it was carried. This was all perfectly within his legal rights, although it didn't endear him to the senatorial class--luckily he had Pompey and Crassus to watch his back. The first occasion is a different matter. It's hard to figure out what the hell Cato's argument was, since what Caesar was asking for was probably not illegal and technically speaking probably did not actually require senatorial permission, but probably what's supposed to have been going on is the consuls, who accepted candidates' professiones, referred the matter of accepting Caesar's professio to the senate and Cato opposed its acceptance. Legally this is of a totally different character. No law is at stake here, only the individual actions of the magistrates accepting the professio.

Anyway, so much for the legal context of these two incidents. You ask why it was not more common practice, I guess supposing that Cato was the only one who did it. He was not. There was technically no limit on how long a speaker could occupy the platform, and speakers used this freedom to digress and waste the day (as Cicero calls it, in some variation or another) with some regularity. I know of at least two cases in 57, in October and December, when Publius Clodius attempted to speak out the day, to no success--in both cases Cicero says that the senate shouted at him to shut up, the first after he had been speaking for nearly three hours. Cicero himself never tried to talk out the day (although his delivery of the In Pisonem must have taken four or five hours, but this was probably an oratorical tactic to make Piso squirm under the weight of four hours of invective--it probably helps that Cicero had no good case against Piso), but he does praise the tactic, saying in the de Legibus that although overly lengthy speeches aren't good the exception to the rule is if the senate is trying to pass something ridiculous and this is the only option left for the orator of prudence--in this passage he praises Cato's skill in being a bag of wind.