Why MACs are so important despite digital signatures doing everything a MAC can do and more
There are many advantages of MAC's over signatures.

For signatures you need to use asymmetric key pairs. Public keys need to be trusted for this to work. Unfortunately establishing trust is not that easy. Furthermore you don't want to use a private key stored on, for instance, a smart card (which would require a PIN and would likely be too slow).

Instead you can simply agree an authentication key (or a key for an authenticated cipher). This allows much more efficient operations both regarding


the speed of calculation of creation and verification of the authentication tag / signature and
with regards to the size of the authentication tag / signature.


For many protocols the problem that the receiver can also spoof authentication tags is not a (huge) issue. It could be a bigger issue for protocols where the two participants use the same authentication key for both sending / signing messages and receiving / verification of messages. TLS, to name just one protocol, uses separate keys.