Bluetooth symbol is not visible in the status bar after updating to iOS 12

Not what? Not-you didn’t bother to read the answers already posted?

I can’t see Bluetooth sign on the top of my phone after resetting.

This is a technical support forum, not a debate society.

If you're not apple with Apple's decision, then tell Apple. The question has been answered. We can't change it. We are not Apple.

Also a correction to another of your points. When you had the BT symbol on your home screen, it did NOT tell you which device was connected via Bluetooth. It ONLY showed that Bluetooth was enabled in settings. So other than telling you Bluetooth is actually enabled you never had more information without having to go to Settings > Bluetooth to see what device is actively paired.

I'm not sure which phone model you have? Admittedly, I'm going off the last year with iPhone X and now with XS Max. On iPhone X, nothing other than a BT Symbol was shown. Apple made the change for all phones in iOS 12. Likely because XS, XS Max and XR all follow the same design layout of iPhone X and is how iPhones now look and operate. I'm not here to argue at all. You seem to be under the impression your posts here will result in some change. It doesn't matter whether I'm not unhappy any more than it matters that you are unhappy. Provide your thoughts to Apple via the link I respectfully provided.

When you purchase this forum, you can tell me what I can post or not post. Until then, I'm just as welcome to post as you are.

The simplest solution is to turn off Bluetooth on your phone. You can do that easily. Otherwise you you've got to be kidding me, right? And if you're not kidding me, you shouldn't own a Bluetooth enabled phone. I'm sure there's a good flip phone you can own. One that doesn't connect to your car system, or let headphones pair with them. That would be the best solution for someone as paranoid as you.

Updating the iOs.

I can’t see Bluetooth sign on the top of my phone after resetting.

If your using iOS 12, your phone is working as designed.