Drains that connect your home to the City sewer lines are only big enough to carry water, toilet paper, and human waste. City sewers and pumps are sized and designed to dispose of very specific things. Using your toilet for disposal of many modern products will often result in blockages.
Many items can cause clogs, sewer backups, and overflows that may damage property and the environment. The City maintains and clears City lines up to the curb. Homeowners are responsible for blockages and clogs at their own residence to the curb.