Taxes can be cut in such a way as to tie into David Cameron's desire to show the Tories are being pro-family and compassionate. If the nil rate band were to be raised to, say, £10,000 each and every taxpayer would benefit - but the greatest benefit would be felt by the lowest paid. It would therefore be socially just as well as electorally popular. It would also be philosophically the right thing to do.
I know there's a number of very clever tax people who read this blog. Anyone care to enlighten us as to how much that would cost to achieve?