Right about February gardeners stream into their gardens with loppers in hand and begin pruning hacking up their crape myrtles. Where gardeners decided this is the proper way to prune crape myrtles I do not know. I suspect gardeners took their cue from the way the Department of Transportation pruned crape myrtles along interstates decades ago, but that is another story.
It is butchery.

A great blemish of southern landscaping is upon us: The annual “pruning of the crape myrtles”.
Why the need to control our plants so rigidly? There are a great number of gardeners who actually believe that trimming and shaping plants is required for the plants’ good health, nevermind that these same plants survive just fine in nature without us.
I would suggest that it is our need to control our world. Perhaps there is a belief that the landscape is there to be bent and torn and rent according to our explicit view of what is beautiful. The truth is much simpler I suppose: We don’t think about it at all.
It’s a pretty plant. My neighbors do it. Where are the loppers?
Pollarding
Used since medieval times, the technique of removing the upper limbs of a tree every season is called ‘pollarding’. It was (and still is) used in Europe as a method to control height, to provide wood for fires, and to provide fodder for livestock. Pollarding can also be used to provide architectural drama to the landscape.
With few exceptions, plants should be allowed to retain their natural form and reach their natural size.
Gardeners who prune their crape myrtles by hacking off the top limbs every year believe this technique will produce a nice crop of flowers every summer while controlling the size of the plant.
Such harsh pruning is not required to ensure a high quality of flower each year, and if we have to prune a plant in a manner that ruins its form in order to keep it the right size…we have the wrong plant.

Prune crape myrtle correctly: light touch
There are two basic methods for pruning crape myrtle, depending upon whether the gardener wishes to grow a shrub with many stems or develop the crape myrtle into a multi-stemmed tree form. Both of these methods are also straight-forward.
- Pruning crape myrtle as a shrub – select a plant from the nursery that has multiple stems. As the plant grows allow new stems to develop. If desired, prune back by 1/3 each winter to preserve size and shape.
- Pruning crape myrtle as a tree. For a new crape myrtle, prune all but three to five trunks off at ground level. Yearly maintenance should include removing branches that rub or cross.
–How to prune a crape myrtle to preserve natural form – Dr. Jim Robbins, University of Arkansas
-A great article on pruning crape myrtle correctly (including the difference between topping and pollarding) from The Pruning School.
Formal gardens and highly architectural designs often use sheared or shaped plants to great effect.

While I agree with your general comments, I submit that the street trees shown would be better off with some interior thinning to promote a healthy crown and mitigate any deleterious impacts from crossing branches