I‘m pretty sure Apple won‘t do that, because they want you to buy your kids their own iPhone.
Why doesn‘t the iPad have this sort of multi-user mode? An iPad is the perfect device for sharing. But no, if you don‘t want your kids to read your emails, you need to buy them their own iPad.
> if you don‘t want your kids to read your emails, you need to buy them their own iPad.
You're right. But I still think I would buy my kid their own iPad even if my iPhone/iPad had a kid mode. My kid has their own iPad and I still find times when it would be ideal to give them access to the basic features on my phone/ipad. Frankly, if iOS just added the ability to password protect any app then that would be good enough, and it would be useful for more than kids... hand you phone to a coworker or relative to look at photos they can't accidentally/intentionally hop over to your email.
Your last use-case is sort of covered by Android's screen pinning feature[0]. You have to enable it in settings, but it's useful, and seems to work well.
Why doesn‘t the iPad have this sort of multi-user mode? An iPad is the perfect device for sharing. But no, if you don‘t want your kids to read your emails, you need to buy them their own iPad.