The Real Bev wrote, on Sun, 13 Dec 2015 21:05:30 -0800:

Dot? Explain...

It's part of the match mounting process to ensure the least amount of
imbalance at the time the tire is mounted on the rim.

Yokohama, for example, here's a verbatim quote from Yokohama:
http://www.yokohamatire.com/tires-10...match-mounting
"To facilitate proper balancing, Yokohama places red
and yellow marks on the sidewalls of its tires to enable
the best possible match-mounting of the tire/wheel assembly.
There are two methods of match-mounting Yokohama tires to
wheel assemblies using these red or yellow marks:
- Uniformity (red mark)
- Weight (yellow mark)"

When I mounted my tires myself, I used the red-dot method (which
always takes precedence over the yellow-dot for the brand of my tires:
https://www.ehow.com/how_7783097_mou...s-red-dot.html

Here's a decent description:
http://www.sumitomotire.com/assets/p...nce%20DOTS.pdf
The Balance Marks will be indicated as follows:
Yellow - Within 3 inches to either side of the YELLOW circle is the LIGHT
spot of the tire. Each tire is confirmed at the factory for
radial balance, and marked at this point. For most mounting
practices, Sumitomo suggests mounting this YELLOW circle near the
valve stem, and use of industry recommended procedures for safe tire mounting.
Red €“ A RED circle denotes a measurement of high-speed run out (measurement called
HARMONIC). If the wheel/rim is an OE spec rim, it is marked at the factory
with a DIMPLE (in the rim/wheel heel). If this tire/rim assembly gives a
vibration at high speed with the YELLOW circle at the valve stem and the
bead is checked for proper seating, then the RED circle should
be matched with the DIMPLE.

So, notice a few things:
1. It's "work" to figure out what the dots mean, and work is effort which
the tire monkeys don't feel like doing.

2. In the end, they "compensate" for their lack of effort with more weight
when they dynamically balance.

3. In "my" (limited) experience, proper match mounting to the wheels (mine
are BBS rims), allows for very little weight to be needed, and almost
perfect balance before you put a single weight on in the first place.

NOTE: I'm very well aware that lazy people say it doesn't matter whether
you match mount or not; but notice those are the people, who, in
general, don't *understand* this stuff, or, who just plop on weights
not caring how many they add or where, just so long as their machine
is happy.