Spideypool vs movies
Have you noticed that in all of the 3 cinematic incarnations of Spider-Man start him over again as a teen? They do that because this character is the most interesting at that time in his life, balancing superhero stuff with school and growing up. Filmmakers choose what works best as a movie, so the Marvel Cinematic Universe is different from the main comic storyline, canonically known as dimension 616, because what’s best as a movie might not be best as a comic, and vice versa.
What works best for Deadpool movies is him being an adult who buys guns, drinks, and loves sex, because he’s a devil-may-care, morally neutral hitman, whose writing relies on comedy and gratuitous vulgarity.