The gate closed behind you protects a place you are only passing through.

Some obligations belong to the situation rather than to you. Closing a gate costs nothing and keeps animals where they should be, and you will never meet the person whose morning it saves. Most public decency works like that: small acts on behalf of strangers, in places you have no stake in. Nobody checks, which is precisely what makes it worth doing.

Look for one of these this week, the trolley returned, the litter picked up, the light switched off behind you. Do it without mentioning it afterwards, since telling someone converts it into something else.