That’s something I noticed a while ago: all podcasters have those huge microphones in front of them - sometimes with a gigantic boom - that wouldn’t look out of place on 1950s TV. But unlike in the 1950s, they’re not trying to hide them, no no: the more visible, the bigger, the better.
I can’t figure out the point of that prop. If I did a podcast, I’d try to unclutter the shot myself.
audio is usually processed digitally; these XLR mics all filter their input through a preamp, but a digital process won’t directly capture audio the same way a physical diaphragm in an XLR mic will, which is what the podcast microphones OP is asking about use.
companies can produce smaller microphones and a lot of people use smaller microphones that capture and process audio differently then XLR mics, but if you’re curious about why podcast microphones specifically are physically larger than other mics, it comes down to the function of a microphone diaphragm designed for the human vocal range and its supporting components shown in the video linked above.