Why do abstract classes need constructors?

Question

C++ / C#

Hello everyone!
I came across this code

abstract class AbstractClass 
    { 
        public AbstractClass() 
        {
            ...
        }

    }

The code is, of course, conditional. The main question is, what for an abstract class constructor? I still don’t know c# well, but it’s impossible to instantiate such classes like them. Maybe this is nonsense, who wrote it?

Answer 1

So that in each constructor of the heir, do not write the same thing.

Answer 2

If some other class is inherited from an abstract class, then why not specify the fields and methods of the abstract class without using a constructor?
Like this

abstract class AbstractClass 
    {
     public int field = 1;
     public void Method();
    }

    class ConcreteClass : AbstractClass 
    {
        public ConcreteClass() 
        {
               public override void Method()
        {
            Console.WriteLine("Реализация");
        }
        }
    }