Some people have astigmatism that is most likely not lens-induced.
Usually those are coming from high or moderate myopia.
Genetics, other influences not related to healthy attitudes will not be listed.
Let’s number the possible cases.
1. Eye misalignment: phoria, tropia (strabismus)
From quite a few cases really digged in, I couldn’t find people having strabismus and not having astigmatism. Eye default placement makes a substantial amount of corneal remodelling stimulus, because it happens at least for every sleep time and every time person closes his/her eyelids.
1a. High myopia esotropia strabismus or esophoria caused by LR-SR band thinning
Corneal remodelling mediators such as rectus muscles are simply off from their anatomical position and they gradually lose normal tones, resulting with over- and underaction of certain muscles.
I suspect to be the cause of my astigmatism if I indeed have this pathology.
If I have, muscle union surgery should fix my esophoria and astigmatism (gradually I guess and when I will not use cylinder).
The problem listed above also can strip off the ability of high/moderate myopes to do Active Focus, since there is no evidence extraocular muscles are not involved in Active Focus process.
2. Ciliary spasm
It does not exceed -1.50 DC. It should cease with cycloplegic drops instilled. If not, ciliary spasm could not be proven. As well, differentials of course will reverse both. There might be a possibility for this astigmatism to be in top of other.
3. Presence of ATRSA without correction
Against-The-Rule Spherical Aberration (ATRSA) is my term not used in research. Existence of it can be proven using n=1 experiment (myself). Not sure it is caused by eyeball optics or spectacles.
4. Functional Astigmatism
Dr. Forrest describes about this one. It is caused by tendencies of using some eye movements or unequal sight over the opposite becoming abusive in certain individuals.
References could be requested via replies.