There are 4 issues that I find with this idea.
First, as winehq has admitted readily, having WINE installed presents a security risk to Linux users. Because it emulates the run level of windows, it is capable of running (some) viruses as well.
Second, the current 10.10 install CD is so full, they've had to start removing mainstays of Ubuntu/Kubuntu, such as GIMP and aptitude. WINE is a big program, and I don't think the sacrifices would be worth the gain.
Third, running programs in WINE does not always work perfectly. In fact, it often behaves in unexpected, buggy ways that would reflect poorly on Ubuntu as end users go through headache after headache to get something they are installing for comfort's sake. Ubuntu should not risk the general users thinking that Ubuntu is broken out of the box.
Fourth, this would be a great idea if everyone needed WINE, but honestly, most people who use Ubuntu find free alternatives to what they use in Windows, and many of those alternatives are superior. Perhaps them not having the option during install is annoying for a few minutes while they hunt the Software Center for WINE, but when Mac users install Mac OSX, do they expect to have their Windows software working out of the box? No, they understand that they are on another OS, and therefore they have different expectations. Perhaps it would not be unhealthy for Linux users to have a similar viewpoint. If the user is not installing Windows, why should they expect to run Windows software out of the box?