Are lens's protectors needed?

The use of a thick case like the MagSafe leather one will give some protection, but for full protection you will need to look at the aftermarket manufacturers. I don't use them myself

My advice is:-

Never put your phone in a pocket or purse with any objects like keys or coins

Think twice about putting it in a jeans back pocket (for many reasons including theft and cracking the body)

Fit a glass screen protector and always place the phone face down on surfaces. They can be as little as $3

If you have a dirty job like a builder then look for third-party lens protectors or full enclosing case, but expect to remove them for taking photos.

I would add that you have 60 days from purchase date to buy AppleCare+ which will cover replacement of a smashed or scratched camera lens for $99. Without it you are looking at $549