system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why, if baby formula is basically just fortified powdered milk, does it "go bad" after 1 hour at room temperature or 24 hours in the fridge when reconstituted powdered milk lasts 5 days in the fridge?

Is this all about safety or just a ploy to get parents to buy more formula?
gpt
It's a combination of a number of factors.  First, babies have significantly weaker immune systems than grown adults, so a comparatively smaller amount of bacteria can cause them to get sick.  Second, there's no way to know what environment the formula is going to be used in (in particular, how warm), and bacteria grows faster in warmer environments.  And third, babies getting sick is extremely bad news for anyone selling formula, so they tend to be very cautious in what they say is safe.  The amount of extra formula they sell because of this is probably pretty small, especially compared to the risk to them if they get it wrong and their name gets attached to babies being picked up by ambulances.