I think it's because you'd need a continuous line of magnets over the full tube, as opposed to accelerators at intervals so it's probably orders of magnitudes c

I think it's because you'd need a continuous line of magnets over the full tube, as opposed to accelerators at intervals so it's probably orders of magnitudes cheaper. I don't know about the reliability of compressors but I'd say you could have a couple onboard if they're an issue.