If you have your landlord call the plumber and pay for the plumber and you expect that to happen faster than you could do it yourself(because you are working your own job), then it's hard to argue that is not a value-added service.
If you break the toilet and now consider the property unlivable, due to a broken toilet, that isn't the landlord's fault nor the fault of the toilet. It's your fault.
Accidents happen and your landlord should be cool about it, but it's still your own accident.
None of this applies to natural causes like environmental damage, of course, but a lot of what happens to rental properties is caused by tenants.
If you don't own it, it shouldn't be your responsibility to repair it. The only circumstance in which you should spend money beyond the rent you already pay to fix something that doesn't belong to you is if you broke it and your rental agreement doesn't cover accidents. Homes require maintenance, lived in or not, and a homeowner can decide to neglect that at their own peril. If something goes wrong, it's the landlord's responsibility to fix it, not the person paying them for the service of having a roof. If they don't they'll likely lose a tenant and therefore income, so fixing their investment property is just required investment maintenance, the cost of doing business as a landlord.
I'm well aware many places have laws that touch on this subject, many of which have been heavily influenced by landlords.