Why? Legacy habits. Some advisors still prefer the "old way" because their internal workflow is built around email attachments. "Do you actively use the Lexware Steuerberaterzugang, or will you just ask me to export a CSV anyway?"
If they say yes, you have found a modern, efficient partner. If they say no, you might be paying for a digital bridge that leads to an empty parking lot.
: You handle the daily bookkeeping; the consultant uses their access only for the annual financial statements (Jahresabschluss).