To be fair Kev you could say the same about any piece of equipment we use live. Who will notice the difference between a £100 Harley Benton P or a £4k Pino sig Fender? After all the compression, EQing, speakers, room etc, both will sound like P Basses.
Hopefully you'd notice a difference in how it plays, otherwise indeed, why bother! I doubt at a gig you would notice what a high quality DI is doing to your tone. Or, at least, id enjoy some blind sound tests to see if people are noticing what they think they're noticing
