kids are 'snotty' and they touch everything, wash their hands very little (and not so thuroughly at that), and well, put them in their mouth's and nose's and eyes more than grownups, so day care is a literal 'germ factory' no amount of bleaching will stop the snotty kid picking his nose and then touching a toy, dropping it and moving on to the next, dropped toy is then picked up by your kid, he/she plays then touches nose, eyes, or mouth.
So yeah, this happens at home, your youngest grabs a toy, sticks it in his mouth still and then drops it, your oldest is in charge at clean up and puts it away, yuck! BUT your kids in your house have a lesser chance of bringing the germs in in the first place, you have to introduce the germ..like say that kid who is really too sick to be there, but mom thought dosing him up with medicine could get her at least an hour or two of work.
which is why I say my husband gets the flu shot, and it covers the family
(that same mom went to work sick too....)
And lest you think you have to lock the door all flu season, most people stay home from church when sick, most grocery cart handles have the germs dried and died before your kid gets there (though feel free to wipe it down as needed) Most toys in stores are hard to mouth (though I do recomend washing hands after visiting before eating) So other than school or daycare flu season isn't as dangerous..though busses and the like up the risk..people coughing in a closed environment and all....