Why can't crutches give gifts?

There is such a custom that the son is not allowed to send crutches to the elderly, because the son is the crutches of the elderly, so he can't send them. Daughters and so on can be sent.

Birthday gifts for the elderly can be used as gifts symbolizing longevity and health and expressing concern, such as longevity noodles and peaches, as well as electric blankets, pedometers and electronic sphygmomanometers. Clocks and shoes are taboo. If you send fruit instead of pears, you can avoid the pronunciation of "farewell", "evil spirits" and "parting" that the elderly are taboo. For example: bathroom slippers, seat dual-purpose folding crutches.