Why is two hours the maximum acceptable offset for Bitcoin blocks?

As far as I understand, Bitcoin transactions include a timestamp, but the only requirement is that they don’t differ for more than two hours.

But why two hours? For computers that are constantly synced via NTP, two hours seem like a very big difference. I would expect that a difference of 10 minutes should be enough.

Or, if this is about time zones and summer time, shouldn’t they be using UTC time?

farmers quest to exchange goods and services

i would like to know the possibility to use Bitcoin for farmers to change good and services without ever to use of Money. We are trying to set a network between local farmers and would like to use Bitcoin in exchange for our services.

Looking forward to hearing from you.