Should sysadmins have software development experience (e.g. DevOps)? For what values should 'X have Y experience?' Should we go as far as... "A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new proble…
I see no harm in one having basic experience in multiple fields. Especially when those fields are related. Actually, this concept I kind of "market" it among my circles. A mobile developer should know the basics of web development and vice versa. That way they communicate better.
I claim that already happens naturally. It's our drive to quickly build a niche (e.g. "I'm a professional X developer"), in addition to insecurities that lead to saying "X is not my responsibility", is what gets in the way of expanding our fields of expertise.