Genetic algorithms(GAs): to be considered only as optimization algorithms? Are GAs used in machine learning any way? As a quick question, what are genetic algorithms meant to be used for? I read somewhere else that they should be used as optimization algorithms (similar to the way we use gradient descent to optimize the best parameters search with a linear regression, neural network...). 
If so, why are these GAs not so much present in machine learning (or at least I did not see it too much in the literature)?
Yes, as you found they (evolutionary algorithms such as genetic algorithms) are using for optimization tasks. One reason that they are not using mostly in machine learning could be their performance to converge to the optimum point. Also, implementation of the GAs for some domains could be problematic and it could not be generalized like gradient descent, as it's involved in at least 5 phases‌ (mutation, crossover,  ...).