I'm not familiar with the hoops that Indians have to get a visa to go to the UK, but I don't imagine it's any more stringent than the Schengen area or even the US, which has a much higher bar, needs an interview, etc. But India has no issues giving e-visas to Americans. I'm guessing the Canadian thing is perhaps due to India thinking Canada supports Khalistan? Pure speculation on my part. The end result is India is cutting off its nose to spite its face. Canadians or Brits not being able to freely visit India is not exactly on the top of any Western political to do lists, nor would there be any significant domestic pressure on those governments to relent.

The OCI comment misses the point, as there will always be millions of new former Indian and now foreign citizens and new children of OCIs who would only now be eligible for a card, but may wish to visit India in the meantime while waiting for it to be processed.

I do agree that any PIOs should have long ago converted to OCI but that's an entirely separate issue, coupled with the fact that India keeps extending the deadline to do so. Affects a very small minority of passengers while the current visa issue is real.