SMBs often implement BYOD since they can’t afford to provide employees with devices. Some SMBs have found ways to help mitigate risk without traditional MDM, but it isn’t always easy. In some cases, SMBs opt for forgoing MDM entirely, and this obviously creates a substantial attack surface. SMBs don’t have a means of centralizing control over their mobile devices (and that their employees devices are typically also their personal ones) SMBs are willing to take the risk.”]
Source: https://www.csoonline.com/article/2140823/how-mdm-works-or-doesnt-work-for-smbs.html