I think you misunderstand.
When model libraries offered just a .stl file (and they still do), you downloaded it and then had to slice it for your particular printer. .stl is limited though, it can’t include multi-colour (for example). When users started uploading multi-colour models, something other than .stl was required but there is no common standard file format everyone supports.
.3mf might seem like a common standard, but it is too flexible. Bambu (in particular) started including machine-specific information and formatting within it, so of course if you download a .3mf for Bambu Studio, it isn’t necessarily compatible with the Snapmaker U1, Snapmaker Orca, or even vanilla Orca. I’m sure that’s deliberate, trying to lock people into Bambu.
Who do you mean by “you”? These translation utilities are independent community projects, usually just one interested party with the skills to solve a problem they had and then offering it to everyone else. Snapmaker have nothing to do with it.
For the smoothest UX (user experience), I suggest you try the web browser extension which translates a Bambu .3mf into Snapmaker U1 commands while it is being downloaded. MakerWorld Browser Extension for Snapmaker U1