As an employee I am not your friend. I'm leasing you time out of my life to get your work done. Being polite and amicable is part and parcel of ensuring that transaction goes smoothly but do not be mistaken: you're not getting an invitation to dinner and we're not going on a camping trip together. The deal is in the contract and my obligations end there.
More often than not I tend to go above and beyond the letter of the contract but I've worked for employers who take it personally when I chose not to. I don't have the time or patience for such petulant behaviour and let those bridges burn. My advice to employers is to not get personally invested in your employees; anything beyond the contract is a bonus and you should never expect it. The contract is the contract and as long as everyone is doing their part there's nothing more to it than that.