I live in SE where it rains frequently so I have been saving up rain water and using that only with my plants. Does the fact I am using rain water eliminate the need to check my PH levels? Are there any PH issues when using rain water? My plants seem to enjoy rain water very much.
With the small amount of time it takes to check (2 seconds) why are you concerned with "spending time" checking PH. (harsh comparison) That's like a meth cook saying "oh I have pure red phosphorus, and didnt have to use broken down cold medications and car batteries...... should I bother checking my mixture?"
While acid rain is uncommon, it is not uncommon for a nasty storm to whip up and pick up a bunch of dirty ass debris in the area.
Again. 2 seconds, and a meter is all it takes.
Notice how some days it rains and a car looks dirty. Some days the water drys clean as a whistle, somedays it looks like pure shit and you need a car wash. That means rainwater is very inconsistent.