Why is this an issue?

Marking a variable that is unchanged after initialization const is an indication to future maintainers that "no this isn’t updated, and it’s not supposed to be". const should be used in these situations in the interests of code clarity.

Noncompliant code example

public bool Seek(int[] input)
{
  var target = 32;  // Noncompliant
  foreach (int i in input)
  {
    if (i == target)
    {
      return true;
    }
  }
  return false;
}

or

public class Sample
{
  public void Method()
  {
    var context = $"{nameof(Sample)}.{nameof(Method)}";  // Noncompliant (C# 10 and above only)
  }
}

Compliant solution

public bool Seek(int[] input)
{
  const int target = 32;
  foreach (int i in input)
  {
    if (i == target)
    {
      return true;
    }
  }
  return false;
}

or

public class Sample
{
  public void Method()
  {
    const string context = $"{nameof(Sample)}.{nameof(Method)}";
  }
}