Single player uses:
1. Early game power dino: Sarcos are fairly strong and very easy to tame.
2. Taming mount: Sarcos are aster than they look, can turn on a dime and you can use a weapon while riding them.
3. Aquatic mount: They're even faster and more agile underwater, just beware there is a glitch where they instantly die if they go on land, though it's very rare so unlikely to happen.