This enlightening bit of trivia comes from The Japan SAQ (Seldom Asked Questions):
Q. If there is a waiting list in a restaurant, Japanese people write their names on it not in kanji or hiragana (how they would usually write their name if you asked them to), but in katakana. Why is this? I’ve heard that it is considered less personal to use katakana, but I do not understand why. (I can understand that kana is less personal than kanji, but why katakana not hiragana?)–Question submitted by Tim Gershon
A. Actually, it’s all about legibility. Katakana, being stark and angular, is easier to read than hiragana. Hiragana, being curvy and loopy is easily distorted and a lot of people have idiosyncratic ways of writing it. When they write characters using straight lines, it makes word much more legible. It’s the same reason that people are asked to print rather than write when filling out forms using English.
Addendum. Joe Tomei in the comments has provided an excellent Hiragana & Katakana site that has tables showing more features and forms of both systems than I ever knew existed. Check it out.