why not use vinegar as your acid when pH too high?

[waterbear]

vinegar is only 5% acetic acid. It's pH is around 3. However, the reaction of an acid with a carbonate or bicarbonage material such as marble or limestone is not really that dependant on pH. Even very mild acids can damage them.
Lemon juice has a pH of about 2.3. It is actually a stronger acid than vinegar if you just look at the pH but this is not really accurate!
Chemically even glacial acetic acid, a very corrosive substance, is classified as a weak acid, while muriatic acid is chemcially classified as a strong acid. It had to do with the way it dissociates in water.