It is proper Netiquette to accept that businesses monitor hotspots. Don't think your screen is private in public.
Once you logon to a network you are bound by the terms of service. You are actively participating on a network they provide, regulate, and administer. Often times this comes with a certain level of oversight, which varies by provider
Hotspots generally use software to monitor the activity of patrons. Wireless carriers use software to monitor the activity of users. The type and nature of monitoring depends on the provider and terms of service. Many hotspots provide a disclaimer before access is granted that activities may be viewed by others.
Accept that online activities are monitored in public hotspots because user agreements allow it.