Sometimes we only need a few small functions to be performed, so we use micro-services to play specialized roles as independent members of a larger system.
Which would you rather have on your team: one horse-sized duck or one hundred duck-sized horses? This is a funny mental picture, but depicts one reason that micro-services are such a handy concept for an ever-changing production landscape.
Each service runs in its own environment and remains unaffected by other workers. This is a safe, efficient means to perform small one-off tasks that would otherwise require large, bulky frameworks to accomplish the same goal.