1. Batteries do not respond well to a full charge, as some cells may overcharge). Generally, there is a risk of decomposition of the electrolyte due to temperature and voltage).
2. Batteries are unwell when fully discharged, but only if they are heavily loaded (discharged by electric motor). Weakest cells will be drained, and this leads to damage. On the other hand, if the battery is close to zero but ridden gently - nothing will happen to it.
3. Charging to as low a charge as possible that is sufficient for daily driving is reasonable.
4. You can charge in the 10-50% range as much as you like (or recharge). The Li-Ion and LiY-Ion battery is virtually indestructible in this charge range. It will last longer than the car itself.
5. Batteries may gain a capacity by storing them at low temperatures with a low charge (10% or so). Frost compacts the batteries and interrupts (crushes by shrinking) any Li deposits on the carbon electrode. On the other hand, such a "frozen" battery cannot be charged with DC, as it may harm them. I keep my electric cars in the winter in the cold, not in the garage (I look at the forecasts. If there is an opportunity - they freeze).
6. Most batteries up to about 2015 have 'artificial ageing' algorithms, which protected manufacturers from possible problems (mainly fires) with heavily depleted cells with higher internal resistance. This mechanism lowers the maximum charge voltage depending on the battery's installation date in the car, mileage, number of DC charges, etc. The methodology is similar across many brands but differs in detail - e.g. Nissan Leaf has a different one to Mitsubishi Outlander PHEV).
There is no malice on the part of the manufacturers. How were they supposed to check in 2012 how their battery would behave after ten years? They estimated theoretically, what would happen to it and hedged with an appropriate algorithm. I would do that myself if I were them.