When I was at the kubota dealer I had a key for every piece of equipment that they sold. They are universal, where one key will fit an entire series of tractors. All the L's took a certain key (with exception of cab models, etc), for example. So I purchased one of each of the keys. Ain't but about 9 or 10 total. Then I had a key for every one of them that showed up at the shop "I forgot my key". Cool, I have one let me go grab it and we'll get you checked in.
Point being if you have multiple pieces of equipment, it might be a good idea (as you guys have already eluded to) to have a spare for each one. If they are only giving you one now, tell em you want another one. It's like, what, $10 for most of them? If they can't "give" you one, just buy it and end of conflict. Don't start some crap about "you gonna throw in a spare key or I'm not buying"....that's immature. I don't totally disagree with it being a major turnoff, but if you're signing paperwork and the dealer won't "give" you a spare key, I personally don't think it's a deal breaker, or an avenue to make a salesperson's day a little worse. Ain't a big deal really. Sometimes the dealer managers tell the salespeople that they don't give away keys because the managers are counting every penny, and that's fine. But remember the little things sometimes are what sticks in a customers' brain. Every situation is different as well.
cant' tell you how many of them "I" (personally) have given (and paid for out of MY pocket) to customers over the years to people who've lost their spare(s). And I'm just a grease monkey.