I don't think this is necessarily true in all countries. Here in the UK I see a lot of people using Xero & Sage, and micro businesses using Freeagent.
* Your bank will hate you.
* Your investors will hate you.
* Your payroll system won't work.
* Your tax systems won't work.
* Your accountant won't work.
* Grants are even off the table in some cases.
* Some places won't audit without Quickbooks.