That seems ridiculous to me. You should be out of your seat before the train stops, as the majority of people are. And tables don't really make too much of a difference, especially not on a crowded train. You are literally saving about a second, maybe two seconds of time by omitting tables. Not enough to warrant them not being there in my opinion.
I actually think that the argument stands if the tables were so big that someone going through the core sits in an aisle seats, takes out a laptop and plugs it in.. then the window seat person wants to get off..
But if small tables are fitted, like the 365 ones, then you could put a cup of coffee there and your phone, but realistically won't be able to use a laptop. Thus, the likelihood of someone causing problems is vastly reduced.
These are not Intercity trains where people can be up and ready to get off miles before the stop.
The DfT for all of its faults were probably right to go without tables, but smaller tables (or even fold down cup holders?) should have been considered instead.
All I really want is a place for a drink, or to plop my phone down on. Anyone that wants more could pay the extra for first class (or claim it on expenses). Likewise, if I had to do work and was going to be on the train for longer than 20-25 minutes, I'd consider paying too (if it wasn't the case that the rear end is declassified anyway).