Flight time database

So I do travel by plan from time to time – and everywhere I can find out when I depart (in local time at the departing port) and when I land (in local time on the destination). I cannot however find the (estimated) flight time anywhere, when booking the ticket – why is that? And why isn’t there a simple service, where you can either look up flight times – or at least enter the two time you know and get it calculated on the fly (and accounting for time zones and daylight savings).