Why is this an issue?

It is needlessly complex to invert the result of a boolean comparison. The opposite comparison should be made instead.

Noncompliant code example

if  !(a == 2)  # Noncompliant
  # ...
end

b = !(a < 10) # Noncompliant

Compliant solution

if a != 2
  # ...
end
b = (a >= 10)