Many websites, apps and other stuff one has to use have the default
behavior to automatically reconnect to some host if they are
disconnected. They can easily get confused, depending on the
redirection mechanism which is used. Sometimes you are explicitly
redirected through a HTTP proxy - that is, you at least get an
explicit HTTP redirection header. Sometimes they just use a
transparent proxy, so it appears as if the requested IP address would
answer. Sometimes it just answers the first DNS query with a wrong IP,
which in turn can confuse
Except for advertisement (which I really cannot stand anyway – if I pay for a hotel, then I want to have wifi included, without additional ads), the only reason for doing this that I can think of is to identify people for legal reasons. But then, please just let everyone sign a contract on paper, and just use wpa2-psk. This is a solved problem. The configuration is easy, and it works.
If you really want to send messages to the user, at least write on your tickets which website they have to visit in advance, and reject all other connections beforehand. Yes, this might sound a little less user-friendly at first sight. But visiting a website is something every internet user should know anyway, while leaving apps and programs in an indefinite state can really mess systems up.