It’s unrealistic to expect that you will never accidentally spill water or other beverages on your phone or will never need to urgently text someone outside on a rainy day. Thus, you definitely want your phone to have zero openings and robust internal sealing so that water cannot seep inside and mess with the electronics inside your phone.
Well, that robustness is impossible if the phone’s cover easily pops off or cracks, potentially permitting water to seep inside the PCB—the heart of the phone. Furthermore, high-end phones are even dust-resistant these days. Obviously, no one likes tiny rocks or sand particles getting inside their phone and hampering its functionality. However, it becomes very difficult to make a dust-resistant design with a removable casing.
Room for Other Features
I’ll restrain myself from going too deep into the technicalities of battery design, but to put it plainly, removable battery architecture hogs precious physical space within an already tightly-packed mobile phone. Unlike a concealed battery, a swappable battery requires an additional layer of shielding to protect against day-to-day impacts. This translates to extra thickness. On a phone where every millimeter counts, there is no competitive advantage to compromising for a thicker design when everyone else is attempting to make phones thinner.
Instead of squandering precious real estate for extra battery padding, engineers can instead fit in some cool hardware for empowering the phone, including adding multiple cameras, stereo speakers, wireless charging capabilities or better gaskets for weather resistance.
Supporting Different Battery Shapes
Essentially, removable batteries are also confined to rectangles, or at most, a square-shaped design for easy fitting and removal. If you’re an electronics geek who is aware of recent trends in the battery industry, you know that new phone batteries are being designed to squeeze out more power with unorthodox designs.
For example, one of LG’s flagship phones has a step-shaped battery design. This has allowed the company to pack more battery into the curved corners, which are otherwise wasted with straight-edged conventional mobile batteries. Similarly, the latest iPhone X uses a quirky L-shaped battery for optimum space utilization.