They steal them for the platinum in them I believe, but they might resell. Them too were they are so expensive these days.
They should prosecute the companies buying these stolen catalytic converters unless they can show proof of legal ownership.
On our local news last night:
A local charity organization had catalytic converters stolen from eight of their vehicles:
https://www.wifr.com/2022/01/27/catalytic-converters-stolen-off-barbara-olson-center-hope-buses/