I've pruned the large crape myrtle in my front yard twice in 30 something years, mainly to keep it out of the utility lines and from getting too far out over the lawn. I see some around that are routinely pruned by people who have a clue, which have nice branching structure. Then, there are those that get frequently butchered and look horrible. Kind of like this:
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One neighborhood that I work in routinely seems to have cornered the local market on f'ed up crape myrtles. I suppose they see their neighbors' monstrosities and think that's the right way to do it.