CH32v303 costs more than much more capable ARM based RP2354A
They're probably produced in far greater numbers than most off-the-shelf STM32 or CH32V chips. You've got a huge ready market in hobbyist/educational products as well as the commercial products that have used it as a convenient choice.
There's that whole non-profit/educational heritage around them that likely selects for a different set of defaults and features than, say, a MCU designed specifically to be the controller for a SATA SSD or a $19 Roku clone.
They also have a small product range, as compared to the broad product matrix a lot of the more "commercial brand" MCUs come in. I know even the CH32v30x chips come in several variations multiplied by several package options (which vary enough to impact the features you can realistically use on them).
I highly doubt it. The RP2xxx lacks the built-in functionality for use in, say, a car, and it isn't cheap and fully-integrated enough for dime-a-dozen gadget application. They are great for hobbyists due to their low barrier to entry, but there really isn't a niche they serve when it comes to mass-produced electronics.
This.
Just programming a microcontroller is generally a pain, but a pain that hardware manufacturers can deal with, because they have employees with experience, who can read the long datasheets, get proper programmers and run the manufacturers software packages to program everything.
For hobbyists, you're basically limited to arduinos, esp??/??, and rpi picos, only those are guaranteed to have a lot of software support, documentation, easy availability on aliexpress etc. for cheap, and can be made to actually do some stuff in an afternoon of tinkering.
(technically it's the same with proper RPis, where they're the only SBC board (not x86 baed) that you're guaranteed will have at least some software support after 5+ years).
This isn't quite true, though it's true at the RPi's price point. For example, Toradex (disclosure: I work for Toradex) produces the colibri-imx6 system-on-module that can be turned into an SBC with a stock carrier board. It was introduced in 2014, continues to be supported today, and will continue to be supported until 2036. But that level of long-term support and maintenance costs money, and the pricing reflects that.
Conversely, there are a lot more variations within other MCU lineups. Just looking at the WCH CH32v30x datasheet-- a single relatively low-popularity range from a single vendor, the datasheet shows 9 basic models with five different physical form factors, and there are theoretically different SKUs for different temperature ranges, etc.
I think the CH32v303's single V4F core might be slightly more capable than the Hazard 3 cores RISC-V cores (as it has a hardware FPU), but for everything else the RP2354 is probably better (and the ARM cores do have hardware FPUs)
And yeah, it has its PIO modules, but those aren't powerful enough to make up for it. They are fine as an alternative to bitbanging Neopixels, but you can't rely on some hobbyist's vibe-coded weekend PIO project which takes up all the PIO slices and 30% of one core to do application-critical communications.
I would take an RP2000 in a heartbeat for most of my hobbyist products, but for anything professional an STM32 is orders of magnitudes better, and even a CH32v303 looks like a more attractive option at first glance.