Mostly for support. Companies give trainings on using B2B software so if users are coming with basic questions you can push back to company contact/manager/buyer with: "wtf" your people are trained on using application. Rise the support fee or sell additional training.

For B2C you cannot have any expectations, even if user knows how to use computer or understands basic English or has good enough eyesight to read any text on your site.

Well what we see for B2C companies is usually that they just don't care and you don't get any real support but that is a different discussion :)