Think of all of the things that could possibly fall down your drain. Food, hair, soaps and cleaning supplies all go down our drains. Over time, these items will build up causing slower than intended drainage.
Many products go down your sink every day. Daily bacteria buildup from toothpaste and other facial products create those smelly sinks in your home.
When your drains are free from any obstacles such as food and product buildup, it allows water flow to go through faster. When there are items that get stuck, it can make it difficult for anything to drain down your sink.
If you do not take the initiative to get your drains cleared, it is very common for bacteria and mold to form. Mold and bacteria thrive on moisture, making drains and sinks a perfect place for them to grow.
Like anything else in our homes, drains need maintenance as well. If your drains are never cleaned out, you can expect to have constant problems and may also face long term damage to your pipes.