=== Unordered Lists ===

Two options:

A large majority of wiki engines use an asterisk (*) to denote bullet lists. The multiple asterisk approach for sublists was the first wiki syntax for sublists. Users do not need to count leading spaces like in markups where a sublist level is determined by the number of its leading spaces.

Ignoring the indentation makes at least the first-level (most common) lists
work across practically all wiki engines that use asterisks for lists, and is also friendly for users who indent their lists reflexively.

Multi-line and multi-paragraph lists are too rare and complicated to include in core standard.

Hyphens (-) were not chosen due to the following reasons:

# asterisks are overwhelmingly more popular in current wiki syntaxes
# if you have a list of numbers, how do you know which numbers are negative?
# many people sign their names on wiki using a hyphen or a double hyphen
# dashes are used to write dialogues

=== Ordered Lists ===

Two options:

The number sign (#) is used for ordered lists in most wikis. Using the same rules as for unordered lists makes it easierto learn and remember the markup.

The number was not chosen as it defeats the point of having ordered lists, since you have to number your items anyway.  Also, you would have to type two characters instead of just one.