Why does spaghetti sauce get watery when put on cooked pasta?

Spaghetti sauce contains a lot water content. When cooked pasta is added to spaghetti sauce, the pasta absorbs some of this water, causing the sauce to become thinner and more watery. Additionally, the starch from the pasta also acts as a thickening agent, which can further thin out the sauce. To avoid this, you should try to cook your pasta al dente, which means it is still slightly firm to the bite. This will help to prevent it from absorbing too much water from the sauce. You should also add the pasta to the sauce just before serving, and try to use as little pasta water as possible when adding the pasta to the sauce.