three is the magic number

Why is it that there is always one member of any three piece band that I can never remember their name. I thought it was me but then I started asking some people to name all three members of some well known three piece bands and only a few people actually knew all three. Pretty much everyone could only name two of the members and then stumbled on the third.

Here's what I could think of. I mean..maybe it's just me.

RUSH
Geddy Lee, Neil Peart and whats his name.

THE POLICE
Sting, Stuart Copland and whats his name.

THE MINUTEMEN
D. Boon, Mike Watt and whats his name.

NIRVANA
Kurt Cobain, Dave Grohl and whats his name.

ZZ TOP
The two dudes with the long beards and whats his name.

THE JAM
Paul Weller, Bruce Foxton and whats his name.

GREEN DAY
Billie Joe Armstrong, Tre Cool and whats his name.

DRYER
Rachael Sunday, Joel Lilley and whats his name.