If you don't need them with laptops why do they specifically sell them for laptops?
They are useful when connected to commercial power which can have high voltage spikes. That is what a surge suppressor does, it clips voltage so that a sudden rise to 5000V for 10 cycles will not kill your machine.
A suppressor does not regulate voltage in the sense that it would take a drop to say 95 volts or a surge to 130V and bring it back to 115V. That is the risk faced on a train or a plane. With laptops powered through an adaptor, that kind of variation is not a problem. So, a laptop in your home or office plugged into a wall socket should be protected by a surge suppressor. That is even true when travelling in a hotel or airport (even though I simply plug in the machine and do not carry a suppressor). But, without the high voltage spike risk of commercial power systems, I have never heard of a compelling reason to use a suppressor on a train or plane. It does not do anything.