It's also each traveller's responsibility to act in a way prior to travel which keeps them as healthy and "match fit" as possible. Especially, if you are travelling internationally and would incur large costs (relative to your funds) and/or your schedule is inflexible (e.g. important meetings or events), you avoid all reasonable risks.
For the unfortunate surprises there's the TI to cover the rest. Though, the insurance industry needs to pull their weight, as well, instead of attempting to obstruct and obfuscate claims(1). While the cheaper tickets are appealing in cost, the buyer also makes a known decision to fork up money should their situation change. As long as airlines offer also tickets with low-cost or free changes, I'd suggest they should not need to routinely offer waivers for the lower booking classes, In fact, it's great that they already have the 'compassionate grounds' process and that's worth keeping for its own purpose but for your (reasonably) avoidable illnesses, etc, it should not be necessary.
(1) Back where I grew up, insurance companies were legally mandated to settle claims within 1 month from receiving the necessary paperwork, e.g. doctor's certificates, building inspector assessments, whatever they required. The system worked well and the companies were geared up to resolve matters efficiently instead of dragging everyone's feet. I wish we had a similar approach in Australia, too.