We live in a flat and I've never got anything burned from a surge.
Actual burning of components usually results from nearby lightning strikes, or high voltage conductors coming in contact with low-side conductors, or communications lines/hardware. These are "relatively rare" occurences, but they do happen, and are quite expensive to recover from. (Been there. Done that.)
Is it possible for surges to not do instant damage?
Yes. Both surges and sags can cause low-level damage that does not immediately impact the operation of equipment. You just don't see it at the time.
Can they damage the motherboard over time without burning it?
Absolutely, but it is the power supply that is most susceptible to this kind of cumulative damage, and cheap power supplies do pass that damage along to not just the motherboard, but every other component that is connected to the power supply.
Ideally, you should operate a computer system, in its entirety, on a high-quality UPS.
The best you can do for an acceptable second best, is to go for a power line conditioner/voltage regulator, and hope that you don't have regular to semi-regular power cuts. However, you have to remain aware that the majority of power line conditioners/voltage regulators are no solution to profound line voltage sags and drop-outs, and those are the mains anomalies that are hardest on power supplies.
Almost no solution at all is a surge protector strip. Sure, they will filter-out minor spikes, and that's never a bad thing; but the line hits that will hammer your computer system will come straight through a surge protector strip.
Worst of all is running a system straight from the power mains and, in some localities, you just can;t do that without damaging the system.