I don’t think it is not considered a legitimate health issue, otherwise those conditions covered by higher level extra covers would fit into the same basket.
The problem possibly is that the health insurance industry tries to simplify cover by bundling extras together…as you have found.
The alternative solution would be to have fully customised cover whereby one could opt in to various extras (say similar to contents or car insurance where individual items of specific value can be included int he cover, as well as specific type of cover for specific household items). The challenge with this would be that it would be very time consuming for one to compare policies with some extras opted in with others not taken up. Also, some health insurers may not be willing to separate some covers which are similar but may not be relevant to one specific condition…otherwise one may have scores of choices of extras which one needs to chose when taking out cover. Insurers may also place a higher premium on those which specifically select cover for pre-existing conditions or may refuse cover for such conditions like the travel industry as it could be seen the customer is trying to take advantage of the existing cost spread across all other policies.
I also expect that if a customised cover was taken out, this would also lead to later confusion by the policy holder to what has been covered, what they thought was covered but isn’t and what isn’t covered. Such would give rise to complaints and/or greater government intervention which may lead the industry back to a bundled approach like there is at the moment.
A question though, did you ask your health insurer whether it was possible to say take out a basic level of cover with psychology included as a single extra? It would be interesting to know if they allow such flexibility or only take the bundled approach.
The other point is a bundled approach will not suit everyone as everyone has individual needs. So anyone with an existing or unknown future health condition would be in the same boat where cover is not included in the lowest level extras cover.
In relation to travel insurance, the costs for treatment overseas can be horrendous and if there is the likelihood of the requirement for a pre-existing condition when travelling, this means that the insurer burdens all the risk. While it would be nice that all travel insurance was the same for every traveller and everything was covered, if this was the case, we possibly would all be paying much higher premiums for such cover. As you have found, some travel insurers will cover pre-existing conditions, but such cover comes at a price to the individual policy holder.