I think it would be hard to answer that because most everything, if not all, have some drawbacks. Also, the reason can be subjective. I hate it because I hate it.
Being sent on the weekend when the office was closed
Not sent to people that it should be sent
Language is off
User's email account or the business email server may be hacked, so sending an email from a legitimate account doesn't guarantee legitimacy. I would lean toward being suspicious that the person was trying to get basic personal info (address is probably not a big deal) and if your responded, a more financial-related/personal information from you.
I think it would be hard to answer that because most everything, if not all, have some drawbacks. Also, the reason can be subjective. I hate it because I hate it.