USB microphones are becoming more and more advanced, and the gap in sound quality between them and XLR mics is definitely getting smaller. One reason you might still consider getting an XLR microphone is that it doesn’t automatically convert an analog signal into a digital one the way that a USB mic does, and you can use an XLR mic in a non-computer setting. An XLR mic’s signal remains balanced throughout its connection, which is conducive to higher quality sound, especially if we’re talking about high end XLR mics.
While most USB mics have preamps built into them, XLR mics don’t, so you are given a bit more freedom to tailor the sound of the recording to your liking with XLR mics. For amateur sound producers, this is less of a big deal, but all experts started out as amateurs once. If you’re getting invested in the world of recording, starting with an XLR from the get go will make it much easier to upgrade to higher quality equipment, like a pricier audio interface, in the future.