Bonding polyurethane material to glass is unlike encapsulation. Bonding material to glass utilizes adhesives and fasteners which add an extra step to the manufacturing process. Extra steps in the manufacturing process add to the overall product cost to manufacture.
Bonding is less secure than encapsulation because the adhesive material can be removed. Bonding material to glass also increases the chance that normal wear and tear will breakdown the bonding adhesive or remove the bonding material from the glass.
Because there is the potential for bonding adhesive breakdown, lessen the glass seal properties. For example, consumer product refrigeration and freezers need the best seal possible for long term consumer quality satisfaction.