The sides of any turret can be penetrated by any tank easily.
There's a reason all tanks are the most heavily armoured in the front.
I will expand on this:
Tanks don't travel alone, they stick together in platoons of 3-5 tanks. Which there is a Command tank and several other tanks travelling as a group. Because of this, they usually engage targets in a line or v formation. Which makes it harder to flank a single tank because they are all watching each other's back. Plus the front is more likely to get hit.
Example showing MBTs and IFVs.

Another issue:
Armor adds weight to a vehicle. The more RHA you have, the heavier you are. The heavier you are, the slowly you move and you are more likely to sink into mud. Plus not all bridges were built to with stand ultra heavy metal monsters.
One more gripe I have that people miss label vehicles. Basically people assume that anything with tracks is a tank, which has lead to people calling things like "artillery tanks", "Tank Destroyer Tanks", "Anti-air Tanks", etc.
Here is a list of common terms:
IFV: Infantry Fighting vehicle. Designed to carry troops into battle and provide support for infantry and forces in the area.
BMP-1:

M2 Bradley:
SPG: Self Propelled Guns. Basically mobile artillery designed to shoot, then move to avoid counter battery and keep up with advancing forces. Some are armored to protect against Shrapnel and small arms fire.
M109:

152mm SpGH DANA:
SPAAG: Self Propelled Anti Aircraft Gun. Similar to the SPG, armed with either flak guns, auto-cannons, or a combinations of guns and missiles.
Gepard:

zsu-23-4:
TD: Tank Destroyer. Basically a vehicle designed for killing tanks. Usually armed with a gun or a guided missile(Anti Tank Guided Missile/ATGM). These vehicles should not be confused with tanks.
Raketenjagdpanzer 1

IKV 91:

More too come.