Poor Hygine
Wearing dirty underwear, inadequate change of tampons or sanitary pads, not taking regular baths, poor toilet hygiene, risky sexual behavior or activities, and so on are sure ways of promoting the growth of harmful bacteria in the genital tract. These unhygienic practices can also facilitate the introduction of harmful bacteria into the urinary tract which can eventually lead to bladder infections and any other kind of urinary tract infections.
In summary, bladder infections can progress to complications like kidney infection and kidney damage if left untreated or treated poorly.
References:
[1] https://www.webmd.com/urinary-incontinence-oab/picture-of-the-bladder
[2] https://www.medicalnewstoday.com/articles/68511
[3] https://www.healthline.com/health/urinary-catheters