The culture that uses the colander most is the Italian. Colander has a prominent place in the Italian culture's kitchen habits because the Italians are well known for their love of pasta and for having a set of kitchen items that are specifically designed to cook and serve it correctly.
While not all Italians use colanders when cooking, many do drain off excess water from fresh pasta. There is also a tradition in some parts of Italy of making and serving 'ugly' or artisan pasta, which is usually served with sauces that are meant to be clinging onto the pasta.
Besides the Italians, Greeks also use the colander extensively.
There are also plenty of other cultures who use them as well, including people in India and China.