It is not designed as a handhold, it is hinged at the bottom while the top is lightly fixed so it can be easily unhooked and emptied. When it is grabbed by a passenger it is dislodged and its contents are spread over the floor.
There are signs in the bus advising passengers to ring the bell and remain seated till the bus stops, but most people ring the bell and start walking towards the front when they want to get off. The drivers are supposed to wait till passengers are seated but they often start moving as soon as they have issued the last ticket. Standing is allowed downstairs on most buses so there is always a risk that someone will need to grab something to steady themselves even if all drivers and passengers follow the rules.
The general principles of the machinery directive (2006-42-EC Annex 1) require the designer to consider intended use and forseeable misuse. The same principles should be applied to the design of any product. In this case the Used Tickets container should have been located in a place where it would not be grabbed, or designed to be grabbed safely.