However there is definitely a need to protect the keyboard. Nokia handles this electronically rather than mechanically. One can still answer the phone with the Keyguard active, however. I habitually keep the Keyguard active since I also carry my phone in my pocket. Personally I find it convenient and use it, relying on the Keyguard to protect me from unwanted redials.
Life imitates fiction.
I don't want calls from your sales contacts.