Why is RT-LAMP testing for COVID not more widely used?

We're currently in the UK visiting ailing relatives, and travelling here has been quite an undertaking, what with all the COVID testing and documentation to deal with. But we have managed it (although how people who are not vaguely tech-savvy and at least moderately educated I don't know). We have one more hurdle to jump through as regards testing, and that is the self-administered PCR test withing 72 hours of our return to Canada, and we have that waiting ready to go.

But I notice that Air Canada are offering (for Aeroplan members at least) RT-LAMP molecular tests that can be bought in Canada and taken with travellers, to be used before returning to Canada. The tests are self-administered in combination with a Telehealth Canada video session (so, yes, you need to be at least a little tech-savvy for this too). Results, though, are available within 45 minutes, which reduces the stress of waiting for a 24-hour or 48-hour result from a regular PCR test. 

The Air Canada "reduced" price for the RT-LAMP test is $149, so about the same as the pre-trip PVR test test did, although still not cheap, and more than the UK PCR test we booked. It might be a good option, though, for countries where testing is more expensive, or just difficult to arrange. And, yes, the tests are accepted by Health Canada for travel purposes.

The RT-LAMP test - the full name is reverse transcription loop-mediated isothermal amplification test, hence the shortened acronym - is pretty accurate according to studies, comparable with the gold standard PCR test. So, I wonder why it is not more widely known or used?