For Eurostar (Paris<->London) there's a security checkpoint with x-ray and metal detector too. No shoes-off, but you don't have to do that for air travel in Europe either. I guess they're paranoid about the Chunnel...

The legroom on a standard Eurostar seat isn't any better than a plane either.

The Shinkansen, however, really is the gold standard for train travel in the world still: fast, convenient (no security), and frequent.

The fear of a terrorist attack isn't really a reason not to do things. And it's not like it hasn't happened before, remember the madrid (commuter train) and london (subway) bombings?