Why was Bitcoin designed with a decreasing production rate? I have no doubt that the person who designed Bitcoin was many times smarter than me but with the benefit of hindsight was the decreasing number of bitcoins a good design decision given the 'hoarding' it encourages? Wouldn't a steady and low inflation rate increase the incentive to spend bitcoins and make it more attractive to the later adopters?
The main issue with Bitcoin is not attracting late developers, but early developers. At its infancy, Bitcoin was an interesting curiosity - people would play around with it but not necessarily use it as money. But due to its scarcity and many benefits, Bitcoin came to be recognised as a digital currency.

At that point people could either wait and see if it gets bigger, or start using it. If Bitcoin's reward wasn't decreasing, probably a lot of people would put off getting into Bitcoin until it is more stable. If everyone decided to wait, Bitcoin would be going nowhere and fade into obscurity. Nobody would then care for late adopter's benefit. This is why getting early adopters on is so crucial - with them comes incentive for late adopters anyway.