My family was very grateful that I took a shower.
Why are they grateful for that?
Because I come out of the shower clean.
Taking a shower regularly is important to stay clean and hygienic. If you don't clean yourself often then you'll be dirty and won't smell very good, so people might not want to interact with you.
Why does society expect me to smell good?
Because no one wants to be around someone that smells bad. Would you like hanging out with someone that made you wanna gag?