we wash ourselves in wudhu thoroughly, but we become lazy or are in a hurry when it comes to washing our heels.
sadly, we don't wet our heels properly.
its an age old problem, starting right from the time of prophet muhammad (pbuh), for both men and women.
that's why he (pbuh) said
'save your heels from the hell-fire!'
we just have to be focussed and give our due time to every body part, especially the heels, while making wudhu.
if not, then our heels will be on fire!