Dogs last 15+ years. Test the dedication. You get married have kids in 7 years. Up all night with kids, who is up at 6 to walk the dog. How is the dog vet and expense budget when you want to buy a house.

Trust me as a guy who looks after my wife's two pets from her early twenties (before me) full time.

Edit: add the care and lack of flexibility. Hockey game after work, nope home to feed and let dogs out. Vacation, add $$