Question

Why MCB's are used in place of fuses?

Answer 1

MCB's prevent the chances of shock in case if electricity increases MCB fell down and the electricity is stopped preventing any kind of shock. In fuse if electricity increase it may burn the wires or give shock.
Hope it helps

Answer 2

in case of mcbs which are called miniature circuit breaker there is no need to find the faulty zone or it is always easy to find ...while in case of fuses the faulty Zone has to be found with a great effort
and it is electrically safe to hold mcb as compared to fuse .
It is reusable and hence less maintenance cost