Cause, on my V4.5, if it was sick and an adult, with a baby, and I got home, then I keep having to click onto the [!] icon to get it to go away when I have a job, and it makes me play it.
If your tamagotchi already has a tamagotchi job, and is getting the [!] mail again a couple of days later, its rather normal. Your tamagotchi can get another job later around when it's going to leave the baby.
After your Tamagotchi recieves a TamaBaby from either marrying another Tama or getting 1 from the Matchmaker, sometime later your Tama will get another [!] in the mail, this is to get a new job.