Taxes on employers are taxes on employees. Employers have set compensations that include the payroll taxes and insurance plans and everything. Why have an extra layer of obscurity when you could just tax income directly? Unnecessary complication that makes doing business harder just so the taxes are hidden from the working class.
Probably because paying that tax is just extra paper work that doesn't have to be done by the employee. So let accounting of your employer figure it out.
Income tax on the other hand is something the employee will have to figure out himself, because he may have other income streams.
This keeps the work where there is expertise as much as possible.
I don't know the particular situation in Croatia when it comes to how it cross-finances private healthcare but I would assume that this patient was billed for everything they recieved accordingly and not directly subsidized.
Of course there are indirect/externalized cost like the the health worker education system, potentially having hospitals and their equippment set up not to maximize profit but for coverage in the population etc. which this patient now may be freeloading on.
There is another perspective though if you consider free movement of labor in the EU (and to some extent globally for highly educated individuals) and the comparatively low salaries for medical professionals in Croatia and other cost-saving medical travel destinations (Hungary, Poland, Thailand, Mexico and others). If the doctors in the country can make an attractive buck on the side doing private practice then this alleviates the pressure to some extent. Especially if it allows the more senior doctors to stay in country and thus continue to train the next generation in med schools and the facilities.
Now I don't have a source to back it up but my feeling tells me that it is a net-positive activity for the destination countries.
Depending on the scale of business, the foreign money might buy a new machine that other patients can use as well or quality improvements via the international certifications and accreditations.
That is not guarantee against potentially canibalising the local social system and could in worst cases lead to a two-class system so i suppose an adequate system to regulate access and subsidize for social fairness is in place where private and public seem equally "healthy".
Full disclosure: I work in tech at https://www.medigo.com
We help facilitate global medical travel and publish prices to bring the best of capitalism to work in an ethical manner. We also have our own critical illness insurance for global treatment available for employers.
