You could say the same thing with almost any company. Equipment get worn down and maint. capex gets spent to make it last longer, but you depreciate the value on the books. My understanding is that with PPE, you need to be able to prove that the value on the books is equal to the greater of its liquidation value or cash flows it can generate. IFRS provides the option of maintaining the value of PPE at cost or fair value, but if the fair value option is chosen you cannot revert back to a cost basis in the future. Either way, most of the time management does not like the fluctuation of their balance sheet (with values changing in booms and busts). Also the PPE must be revalued each year which has an associated cost.
I'm not an accountant and I'm digging deep into my memory, but I'm almost certain that is the reason.
Also, to answer Laxputs question. Depreciation is a way of matching a unit of revenue with a unit of expense (in this case, the amount of wear and tear required to produce something). Since land cannot be worn out, it becomes an issue of matching expenses to your revenues, and as such land has no depreciation value.