Thank you for pointing that out.
Point is that there are several speakers
and that lecturers are not necessarily organisers ("Contact persons", for excursions) and want to have something to do with it - and again that organisers are not thematic contact persons.
For us it fits like this: The user can decide and we have to live with it. So far this has worked well. We do not (yet) use the registration feature. A simple mail is still enough.