We used to think that "early and controlled exposure is preferable to a first case later in life" for chicken pox, but AFAICT that's no longer widely accepted in most western countries. Chicken pox in children can lead to serious complications in some cases, including bacterial skin infections, pneumonia, and encephalitis. The virus remains dormant in the body and can reactivate later in life as shingles. Now that there's an effective 2-shot vaccine, that's the recommended approach.