Is the sensitivity of case really important? I'm sure most people use their mouse to copy and paste the address.
In situations where people don't copy and paste, it helps to reduce the chance of errors.
Not only that, but the bech32 addresses use BCH codes (well BCH-like codes) which are an error correcting code. Bech32 addresses can detect up to 4 errors when entering the address and tell you where those errors are. They can also correct up to 2 errors (IIRC) but no wallet will actually do error correction for you because that is a good way to accidentally send money elsewhere.