Quality of cut, or cooked properly? If it's the first, find a better place to get a steak. If it's the second, what typically happens is cooks either don't allow for resting, or the steak sits in the heat window while the other plates for the order are being finished. If I want your medium rare steak to reach you at exactly 120 degrees, I need to pull it off the grill at about 112 and allow the steak to finish cooking itself with the heat it is retaining. A lot of the people I've worked with don't seem to get this, and will cook the steak to 120, then wonder why it gets sent back as overcooked.
edit: To add to "why is it hard to get a good steak", another factor is that unless a restaurant is willing to eat a loss, it's tough to offer quality cuts at a price that won't make most customers balk. It's important to realise that for a restaurant to clear a 5-8% profit margin, they need to sell the food for a roughly 400% markup. Most restaurants do not achieve a 5-8% profit margin these days.