Your value of home is the best price in which your home should be sold at, at that particular period. While the prices of homes are mostly tending towards the positive direction, there are also some periods when the market might be experiencing depression and as such most people are forced to sell their home at lower. Going with the valuation at that time might not translate into the best price for your property. Nevertheless, most home owner would always choose the highest price estimate for their property even when shown otherwise, the price at which you would eventually sell would be based on so many factors, which might also be affected by factors that have to do with you.
Another reason you would need to know the home value estimate of your home is that, it would help you put your investment right. Just in case you are trying to invest in some home improvements so that your house can look good for a better sale, knowing the cost of home in that environment can help you know what the new projected sale price would be like even after your improvement.