General Q: What's the difference - LOOKUPVALUE vs connecting two tables and using RELATED?

What's the reason for having both of these similar tools?   Say in Excel we have VLOOKUP and INDEX-MATCH.  But that's (I imagine) due to Excel's age - one tool came first, then much later a better one came out, but we'll keep the old tool because it's well established.  

Power BI isn't that old though.  

I'm comfortable using both, but all I can think of is: 

LOOKUPVALUE is more dynamic - you could say, pull data from a column in Table 1 into a column in Table 2, using say columns 1A and 2A as the connection.  Then you coudl pull different data from Table 1, but this time using column 1C and 2D as the connection.  

On the other hand, if you're always going to be using the same 2 columns to make the connection between 2 tables anyway (which is typical), then connecting the tables, then using RELATED repeatedly, is a bit faster than typing out everything for LOOKUPVALUE. 

Is there more to why we have both of these similar tools?