I have asked myself the same question, before I noticed that EY is basically the Credit Suisse and the SoftBank of the audit world[1]:
> EY has been involved in many accounting scandals: Bank of Credit and Commerce International (1991), Informix Corporation (1996), Sybase (1997), Cendant (1998), One.Tel (2001), AOL (2002), HealthSouth Corporation (2003), Chiquita Brands International (2004), Lehman Brothers (2010), Sino-Forest Corporation (2011), Olympus Corporation (2011), Stagecoach Group (2017), Wirecard (2020), Luckin Coffee (2020) and NMC Health (2020).
In fact, Wirecard managed to partner with EY, Credit Suisse, and SoftBank simultaneously just before going bankrupt.
Maybe because no reputable companies wanted to touch it?
[1] https://en.wikipedia.org/wiki/Ernst_%26_Young#Accounting_sca...