There's this wonderful book, "Corporate Culture & Performance" by John P. Kotter - the biggest take-away for me was that companies under stress to perform will generally cargo-cult their behavior from successful times.

IBM building its own fonts to polish the nooks and crannies of their brand identity may well be such an instance where it is replicating behavior from the late 70's and early 80's of doing everything under the sun. Imho it should clearly not be a priority for them right now.