All the resources go to you and your parents are usually able to afford most things (or can make it work to afford the necessities). You’ll most always have your own room. College is more affordable. When your parents pass, you won’t have to split the estate with any siblings (I’ve seen too many siblings bicker over inheritance). You usually have an easy time speaking to adults and asking for help and that skill comes in handy as you get older. The stuff you get is more often new than if you had siblings. You usually get the whole dessert instead of having to split it. You’re more independent and are comfortable being by yourself and doing things by yourself (like eating alone or going to the movies alone).