Indonesian plumbing and sewers cannot bear the sewage generated in large cities, so most bathrooms do not have toilet paper. You spray (back to front) to clean up; then dry with a tissue. The bidet-style sprayer is inelegantly nicknamed a "bum gun."
In a Western-style household, the toilet may have TP - but you must toss the used tissue into the garbage, not into the toilet. Going out? Take tissues along: they may or may not be supplied.