Being a software tester you might have come across various situations where automation is not advantageous at all and manual testing works better in those situations.
Some examples where manual testing is preferred over automation are:
UI keeps on changing very frequently. If automation is done for this UI it needs to be changed every time the UI is changed.
You have a tight deadline to release the software and so there is very less time to automate so you will prefer to do manual testing and release the software.
So you can see that automation does not solve the problem always, however there are certain situations where automation is very helpful for quality software delivery. Some of the examples where automation is helpful are as follows: