Development is costly, plus the hardware to be built needs to be very simple and cheap. DS80C400 was my original choice, until the other people involved in the project specified that they strictly want something cheap, small, low consumption and not very fancy.

The same people tried to convince me into using AVR, however i am more familiar to 8051, so it will reduce my development time, plus i already have development tools for 8051 thus development cost for me will be near zero in that aspect.