Look at the last ten fonts you actually used. How many came from studying old handwriting? Most are digital systems built on grids and screen legibility. Sketching letters by hand gives you one kind of feel, but it can lock you into organic shapes that fail on a pixel grid. Modern UI design needs fonts made for specific technical problems, not just nice curves.
Seriously, doing it by hand teaches you why the letters work. That eye for detail makes you better at picking fonts later. Your system is useless if you don't know what makes a good letterform. Keep sketching sometimes just to keep the feel for it.