This is exactly the key - residential real estate is based on tons of pricing effects, and appraisals are much more "feels" than "reals", if you will (how people feel about the area, how they feel about the tower the previous owner added, how they feel about the location, etc).
Commercial real estate valuations are almost entirely a mathematical formula based on rents, current, whether they're collecting them or no. And if the rents drop (e.g., you start renting it at a lower square foot rate) the valuation drops, which can require recollateralization (e.g., unlike your house, the banks require that the loan NEVER be more than 50% LTV or something) so if the value of the property calculation makes it go above that, you have to pay down the loan or add additional property as collateral.
Commercial real estate valuations are almost entirely a mathematical formula based on rents, current, whether they're collecting them or no. And if the rents drop (e.g., you start renting it at a lower square foot rate) the valuation drops, which can require recollateralization (e.g., unlike your house, the banks require that the loan NEVER be more than 50% LTV or something) so if the value of the property calculation makes it go above that, you have to pay down the loan or add additional property as collateral.