Say that in you street that are 50 single family homes connected to a same cabin/transformer.
The electric infrastructure powering them (lines, transformer, etc.) has been dimensioned to power them at their average current power consumption rate + something to take care of peaks + something more to take care of eceptions (like - say - a constructions site for the renovation of one of the homes).
Now the existing infrastructure will have no issue with your single electric car charging at night, and probably with that of your neighboor on the left and that of your neighbour on the right, but the moment a given number of families will have an electic car, each of them will try to use 5 kW of additional power more or less at the same time.
That is a lot of "juice" and it sums up quickly.
I believe (correct me if you have better data) that in the US the infrastructure is generally dimensioned for something like 6 or 7 kW per unit, so, adding to each house some "constant" 5 kW (even if only at night) is almost using all the capability of the infrastructure.