If you are a buyer, you are likely to be concerned about spending time and expense on due diligence (in-depth legal and financial research into the business you would like to buy) and lengthy negotiations without having some comfort that the seller will not suddenly decide to start negotiating with another prospective buyer.

To stop the seller from dealing with other potential buyers, an exclusivity (or lock-out agreement) is often entered into by the parties The aim of the exclusivity agreement is to stop the seller from marketing the business to other buyers for a fixed period, so that the you have the opportunity to assess the business within that time period and decide whether to go ahead with the purchase, without the added pressure of having to compete with other buyers.

Exclusivity agreements can help reduce the risk of wasted professional fees and management time on the purchaser. Despite these benefits, it is worth noting that the seller is under no obligation to actively negotiate with the prospective buyer during the exclusivity period, it is merely precluded from dealing with other buyers, and so the seller will be able to effectively sit on their hands and wait for the period to expire, should they so wish.

Clearly this would be a waste of their own time as well, so in practice it does not happen very often, however the point is that the seller is not obliged to negotiate with the buyer, it is obliged not to negotiate with anyone else.