You get arbitrary length arithmetic for free (the 1401 in the Computer History Museum runs a demo program that computes powers of 2, it only stops when it runs out of columns on the printer paper instead of bits in memory). Also there is no alignment to think about and no padding is necessary, which is nice when memory space is scarce as it was and considering the 1401 uses a variable word length instruction set. Plus it's easier to type into a key punch [0] when programming.
[0] https://en.wikipedia.org/wiki/Keypunch#/media/File:IBM26.jpg