To be fair, everyone who is into MCUs has a USB serial converter lying around, if not several. Or more snarky: repurposing a RP2040 is only free if your time has no value.
God, this is a website full of "Hackers" and all 90% of the users can think of is how to get the most money out of the things they do.
I can understand why you would think that, but I can also tell you that I didn't buy a serial connector until years after I started playing with microcontrollers.
I've got Arduino sketches I can quickly flash onto an Uno (or my 2016 HiFive1 320 MHz RISC-V board, which is usually closer to hand) to do all manner of things including UART, flashing a bare AVR chip e.g. ATTiny85 (now supplanted by CH32V003) and so forth.
Same principle as using a Pico.
https://github.com/embassy-rs/embassy/blob/main/examples/rp/...