Why does my mom force me to use sunscreen?

every hot day im about to go outside when my mom says you have to apply sunscreen so i tun to the back door because i hate the way i smell and feel after its applied but she always catches and takes my shirt of and and starts rubbing it on my face feet arms armpits!and stomach and i say ewww as i try to get free and she say hold still and while shes applying she starts tickling me but she says its not her its the sunscreen HOW IS IT THE SUNSCREEN