Is it necessary to discuss the reason of the algorithm choice in my paper?
If you considered others and chose one, then it would probably add to the value of your paper to explain the choice. If you rejected some for important reasons then others would benefit from that knowledge.
But if you just chose randomly, then people will wonder if your work has sufficient value. And if you say nothing, they might wonder why.
If you compared two or more algorithms and got different results, then people will want to know why.
So, I think it is probably a better idea to say something if you can.