As many said already, it can be several reasons like multi-tabling, a bad connection, a strategy to survive the bubble or even to make people nervous.
But do not become nervous about such a situation, better add another table to have some more action.
Usually, I really do not care about such people. Only that I could fall asleep when it is very late.

And I am very sure, that nearly everyone did this already to survive a bubble, at least at
the beginning when they started to play, although it is considered to be a bad strategy, especially when you are short. You want to see still as many
hands as possible to get a good spot again and double-up and the big stacks can outlast you so much longer in such a situation and also stretch their time bank...
I mean, it is completely understandable, if you are in need of money or just started building your
bankroll. But it is better to have good bankroll management so that you can play your game normally.