It all starts with FAR 121.577(a) for part 121 carriers which says:

No certificate holder may move an airplane on the surface, take off, or land when any food, beverage, or tableware furnished by the certificate holder is located at any passenger seat.

Then it gets more interesting -what is the definition of "at any passenger seat". Each certificated airline puts policies/procedures in it's manuals that define how that carrier will comply with this as well as all the other FAR's. Airline A may say that small beverage bottles may be stowed in the seat back pockets (at any passenger seat meaning unsecured) while airline B may say that those items will be collected prior to taxi/take off/landing and that they may not be stowed in the seat back pockets (since that's a part of the seat). As long as both have their policies/procedures approved by their POI (Principal Operations Inspector) they're free to operate with those policies/procedures. Hence, you may see differences between airlines - Mesa may have different policies than US which may have different policies than Republic, etc.

Jim