Since the modern scientific method was invented approximately 400 years ago, not one single repeatable experiment has ever been devised, by anyone, anywhere, anywhen, which has been able to show an "irregularity" (truly random processes such as radioactive decay, quantum weirdness, and Heisenberg's uncertainty principle notwithstanding)
Occam's razor. Entities should not be multiplied unnecessarily.
When Newton discovered his laws of motion, he was right to accept them. When the scientists who followed him for the next 300-odd years accepted them, they were right to do so. Even though he was eventually shown to be wrong by Einstein, until that point, no-one had any good reason not to accept those laws. However, as soon as Einsten came up with new data, came up with new theories, came up with new experiments, came up with new evidence and proved Newton wrong, then scientists changed how they saw motion.
Yes, scientists should always be aware that their theories might not be correct, that there may be an edge case they've not seen yet. But until someone's actually found it, the best you can do is go with what you've got. If an experiment ever comes along to show that the universe isn't regular, science will use that to show how the universe is not regular. Anyone who refuses to accept the new evidence will not be, to all intents and purposes, a scientist. And science might have to do a lot of work to probe the boundaries (if any) of that irregularity and work out how much it affects the millions of experiments and observations that have been done over the last few centuries.
But until that time comes along, it's perfectly reasonable to assume that the universe is regular. Because that's what every experiement ever done has ever shown.
Your black swan argument could just as well be a 10-headed sheep argument. So what if no-one's seen them? No-one's proven that there aren't 10-headed sheep. So it's an absurdity to say they don't exist!
Bollocks.
If you show me a 10-headed sheep, I'll believe you. Until then, it is so mind-bogglingly unlikely that such thing exists that they are not worth considering in any reasonable model of the universe, and you're just engaging in philosophical wankery, not science.