Because it takes advantage of a well-known human tendency to think more kindly of people who have given you a gift. It's a variation of the truth that your customers will tend to think better of your products if they get something unexpected and free along with the product, even if that thing is of low or no actual value.

While this true enough, an ironic side effect of my attending a couple of rounds of sales related negotiation training ( compulsory for everyone at that company ), was to really highlight how calculatingly manipulative this is.

I mean, we kinda all know that anyway, but somehow it reinforced it enough that I know find it actively distasteful.

Even the classic sales approach of buying coffee or a meal feels creepy know, but I've had to relearn to accept it because it's just so hard to fight every time.

When I tell people, the normal response is encredulous "but it's free?". It's really really not, the costs just aren't immediately financial.

(Gifts outside corporate life are generally fine, an actual human wanting to "manipulate" me into liking them more is generally expressing some level of affection. A corporation cannot do that)

Every know and again I get something funny enough that it gets me anyway.. I'm very fond of my all blue Rubic's cube from ibm for example, and I've got a few unbranded water bottles around the place.

Anything else I can't politely refuse just gets binned as soon as I can do so without a fuss.

people who don't enjoy clutter and waste must be still outliers then