Replacing a battery in most modern devices means dealing with adhesive rather than fasteners. The reasons are genuine engineering constraints, even where the result frustrates repair.
Space is the first constraint
A removable battery needs a rigid housing, a door, a latch and spring contacts, and each of those consumes volume that could otherwise hold cells.
Modern cells are soft pouches rather than rigid cylinders, shaped to fill whatever space remains after everything else is placed.
Adhesive holds an irregular pouch in position without a frame, which is how manufacturers convert mechanical overhead into additional capacity.
Sealing requires continuous surfaces
Water resistance depends on an unbroken seal around every opening, and a battery door is a large opening in a critical place.
Maintaining a seal across a user-operated door requires a gasket that stays effective through repeated opening, which is difficult and adds thickness.
Bonding the assembly instead removes the opening entirely, which is why sealed devices and removable batteries largely stopped coexisting.
Adhesive resists impact
A battery held only at its edges can move during a drop, and a pouch cell that flexes or is punctured is a serious safety problem.
Bonding across the full face distributes shock and prevents movement, which is a meaningful contribution to the device surviving falls.
It also stops the cell rattling and keeps contacts from working loose over years of thermal cycling, which is a common failure point in devices that carry a battery loosely.
Cells swell slightly as they age, and a bonded pouch expands against a known surface rather than pressing unpredictably against nearby components.
Not all adhesive is equally hostile
Pull tabs that stretch and release, and adhesive designed to soften with mild heat or a specific solvent, make removal routine for anyone with instructions.
Strong adhesive applied across the whole cell with no release mechanism turns the same job into prying near a component that must not be bent.
The difference is a design choice rather than a physical necessity, which is why repairability ratings distinguish between them.
Regulation is shifting the default
Rules requiring batteries to be replaceable by users or by independent repairers are being introduced in several markets, and manufacturers design to the strictest applicable standard.
Compliance is more likely to be achieved through release tabs and accessible fasteners than through a return to removable doors, since sealing requirements have not relaxed.
The practical outcome is devices that stay sealed and thin while becoming meaningfully easier to open for a battery change.