I think a lot of people buy these amps because they're the biggest and the baddest... Like you said... to impress. I know a few guys that have them basically only because that reason... Neither of them can play them... and niether half stack has ever left the bedroom.
However... I have a JCM 900 that puts out 100 tube watts... equivalent to 300 solid state watts... I have this because I use it on stage. and a 50W doesn't fill the room of a larrrrrrrge bar. 50W will do the job most of the time... but not when you play outside either.... I like the crowd to feel the sound not just get their ears pierced by it. With the high watt amps you get that extra dimension to your sound... where if you hit the open strings in drop d... you can feel it in your chest. The high wattage lets you get a lot of distortion at high volumes with other effects in the loop without the sound turning to mush.... That's why I have my JCM... I didn't buy that until I got all the use out of my little 50W 1x12 JCM 800. I wish I still had that amp though... it was a killer.