I don't think that's quite right, evolution makes trade offs and allocates scarce resources, it's not necessarily because such things would not be beneficial.
It's not clear what "beneficial" means if you consider it separately from the resources required to achieve it.
E.g. it's beneficial to be stronger I guess, and gorillas are always strong whether they use their muscles or not. However for humans nature chose a different path where only the muscles you actively use are strong. This approach seem to work great so far, even though it results in many individual muscles of the body being weak. For each and every of these muscles you can argue that making it stronger would be "beneficial" but as a whole it doesn't seem to work out.
