Just my take on this, with regexp you can create an expression that is the same logically as a equality check using the start of string marker, the string to equate against, and the end of string marker.
Just because it can be done does not mean it should be done.
Regular expression check is like switching to another language midstream that requires extra processing. It is fast to perform an equality match using a hash/exact index but it is much much slower to perform an equality match with a regexp as it has to process the regexp one character at a time and reference the three character splitting index to quickly rule out longer non matches. Regular expressions can also be very bad in some cases that drastically decrease performance but on the other hand inversely increases flexibility of search procedures.
I will have to try to find the best video I ever watched on regexp that really helped me realize why using a regexp as a primary tool of choice is usually a bad idea verses catching all other cases first that don’t depend on regexp and then only using regexp as a last resort. The bottom line of it though was that regexp is it’s own programming language and not just a somewhat universal matching pattern.