"I have often wondered why no other ships came to help and why it took so long for the ones who did."

Actually several ships came to help. The Birma, the Frankfurt and the Mount Temple for example. The reason it took so long was that the ships could not travel that fast. The closest ship was the Californian at an estimated 17-20 miles away. Her top speed was 13 knots which means she could not have reached the wreck site for at least an hour and a half. Assuming that she started for the Titanic as soon as they saw the first distress signal they would have reached the Titanic at around 1:30 at best giving them just 50min to mount a rescue of 2,200 people.

The next closest ship was the Carpathia at 58 miles away. Her top speed was 13 knots and Captain Rostron would later claim the ship got up to 16 knots. We know that it took them three and a half hours to reach the area of the wreck. The Olympic was 400 miles away and could never have reached the site in time.