It just depends on what you load into the drawers. Since essentially the contents of only one drawer at a time is accessible in any case, it's the right UX decision.
Anyway, you need to close those drawers eventually, right? Why not before opening the next drawer?
Put another way, the alternative is to support the general use-case of disorganization: "I'm not sure where the thing I'm looking for is, but I need it in a hurry!" Do you really want to categorically assume in such situations that people have mitigated the tip-over risk in some external way? Just to allow for high-speed riffling?
Your castor idea only really helps if the search happened to start with the bottom drawer first. That's sorta logical, at least in some cases, but I don't think you can come anywhere close to assuming it's going to happen all the time.
Anyway, you need to close those drawers eventually, right? Why not before opening the next drawer?
Put another way, the alternative is to support the general use-case of disorganization: "I'm not sure where the thing I'm looking for is, but I need it in a hurry!" Do you really want to categorically assume in such situations that people have mitigated the tip-over risk in some external way? Just to allow for high-speed riffling?
Your castor idea only really helps if the search happened to start with the bottom drawer first. That's sorta logical, at least in some cases, but I don't think you can come anywhere close to assuming it's going to happen all the time.