Many businesses, especially start ups, choose to rent their premises instead of buying it and the company budget will often not stretch to paying the mortgage on a property. It is far easier to find offices to let than having the responsibility of maintaining your own building.
However, you may wish to consider buying your own premises if the business is going well and if funds allow for it, especially if you are living in an up and coming area. Some of the shrewdest property investments have been made when the price of the properties in the area were very low and are now worth several times what they were, than when they were bought.
It is not a decision to be entered into lightly, but it could well be a good investment for the future, particularly if you have a niche business which means that any premises you use have to be converted for use.
If you rent a building and then have to convert it, for example a brewery, it will be very expensive in the first place and you may have to eventually restore it back to its original condition for the owner.
With the current interest rates, it may not cost much more to take on a mortgage than to rent a place, although you have to be prepared for them to rise.

