I see several reasons and most of these are self explanatory for me: (a) Hotel rates went up during the last few years, more points were issued but point rates were kept the same. Therefore the increase of point rates is a logical consequence, I would not have been surprised if point rates in the past had increased following the general inflation rate. (b) The Dollar (and points are a Dollar equivalant) lost more and more of its value. The prices for international properties went high up but the point rates were kept stable. Again, the increase is a logical consequence. (c) They overdid the Credit Card nonsense and inflated the number of points available for cheap money. To compensate for this prices will go up.

(a) is a general consequence of inflation, (b) is US government missmanagement and (c) is Hilton missmanagement.