Bitcoin is not deflationary, it's inflationary, currently at a rate of 3600 new coins every day, this value halves every 4 years or so, so eventually around 2140 there will be no more new coins.
Well, yes. OK, that point was cleared up. But my original question was why not increase the rewards over time instead of decreasing as long as the end limit remains the same.
It'd give late adopters a reason to opt in?
If only 1 satoshi is generated from the start, today, only 2 satoshi would be in each block. The fees would be hard to calculate and there would be less people using it due to the scarcity of Bitcoins.