It's always more useful to have a team than going solo (as long as you can trust your teammate--and you'd think you could trust yourself, but...) Also it confuses your enemies.

[Jack scowls slightly.] ...It sounds better than "my parents' basement", ok? [Also every proper supervillain has a lair. Not that that's an explanation he's actually going to use publicly.]

[He gets out a little screwdriver and tightens some things.]