Sam didn't need to date anyone!
Spoilers. If you still haven't seen this, where have you been?!!!!
Sam's friends as well as that annoying radio psychologist at the beginning believe the false philosophy that a person who loses a loved one cannot move on until they start dating again.
Sam had already moved on, he was taking good care of his son, he was working, he wasn't depressed, he obviously still missed his wife, but overall he had already moved on for the reasons just mentioned.
Near the very end of the Movie Sam even says to his son that they were fine with just the two of them in the grand scheme of things, they are doing just fine with each other, there's no reason to go to drastic measures.
It was nice that he found Annie at the end, but all in all Sam was fine not dating anyone, he was strong, he had his friends, his son, his home and a job, it was everyone else who was trying to brainwash him into finding a new wife.
It's good for a kid to have 2 parents, but if that doesn't happen it isn't the end of the child's life, there are plenty of happy single parent families, a new wife and mother is not going to replace the previous one, and there's more to life than relationships.
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