I have a lot of cross over between my day job and detailing in regards to pH.
The pH level of soil will determine the success or otherwise of the plants you want to grow. For the most part, plants grown best in neutral to slightly acidic soil, although some prefer the more acidic side, some will tolerate the more alkaline side. No plant will grow in excessively acidic or alkaline soil.
For detailing, different pH levels will do different sorts of cleaning. As a very rough rule of thumb, the further you move above or below neutral, the more cleaning ability you will see.
Most maintenance soaps will be pH balanced, ranging from 7.0 - 8.0 so that they are gentle and safe to use on all LSP's. Some leather and interior cleaners will also be pH balanced to ensure you are not damaging softer, more delicate surfaces. I always cringe at people who douse their interiors with APC for that reason. Neutral products are also safer to use in the sun, and safer on the user as well.
For a long time, acidic detailing products usually centered around wheel cleaners. While that usually centered around products like Meguiar's Wheel Brightener, many iron-removing wheel cleaners are actually slightly acidic too. Acidity also helps with removing mineral deposits and water spotting. Most companies sell acid-based cleaners for this job, Carpro also now sell an acidic soap for this role too.
Alkalinity is usually associated with degreasing, decontaminating and products designed to strip waxes like Capro Lift. Most wheel cleaners are now alkaline, think Brake Buster or Meguiar's Non-Acid Wheel Cleaner. This is also why tire cleaners are heavily alkaline, they are degreasing oils and waxes from dressings and the rubber compound itself. APC's are also alkaline.
Knowing how pH levels work and the values of the products you use will greatly improve your detailing efficiency, allowing you to target specific areas or concerns with more accuracy.