Hi
A friend, HR head, about 7 years ago advertised 4 vacancies in the newspaper, to his horror, he received more than 8000 applications. He was totally confused and expressed his tension during a cigarette break (They were not allowed to smoke within the office premises). I told him to simply draw job and personal skill profiles (Main attributes) and assign this task to few juniors to segregate resumes based on those few very important and essential attributes required for the job. After a few days they were left with applications from candidates who actually were to be called for the initial interview.
That is what happens when resumes (In this case manuscripts) do not comply with job skill profiles (In this case submission guidelines), and those not fulfilling the requirements might be ignored, no matter how good they may be.
It is highly recommended to strictly follow the submission guidelines. Your observation is right, in today's world people should rely more on electronic file sharing instead of relying on snail mail. But, empathize and think from a successful publishers or agents persepective, they probably receive hundreds of manuscripts, so understand their viewpoint and be kind to help them. Wish you all the best. Cheers