It's necessary, for the same reasons you get http://tvtropes.org/pmwiki/pmwiki.php/Main/EconomyCast
Basically, the story is ABOUT certain characters. That's why you can have a story about a couple of vice detectives, and yet they will be involved in every aspect of police work from homicide to SWAT hits, very specialized roles they would hand-off in real life. The story is ABOUT them, so realism is fudged for the sake of them being involved.
Happens all the time in comics. Hulk doesn't become irrelevant in story about flying characters with long range powers. Those characters inexplicably fly relatively close to the ground and zap him from 20 feet away.
Captain America, an infantry guy from WWII, can plan land, sea, air, and space assaults.
And the team science guy can do any science he needs to do.
The story is ABOUT the main cast, so realism has to take a back seat. It's just a little more obvious for the science guys, wheras people don't tend to think very hard about why the ranged flyers are coming so near Hulk, or why Cap can plan assaults way out of his bailiwick.