Why? Because my intent can change. I intend to buy the Empire state building, but who cares what my Intent is? Many traders and Brokers treat a Letter of Intent as if it were holy writ. This is a critical beginner's mistake. As its name indicates _ this document expresses an intent.
On Offer acceptance there is either a contract generated or a pro forma invoice generated. Since the offer is binding once accepted, the offer if well enough detailed and advised can and often does take the place of the contract. Customarily in Real Estate transactions the purchase offer itself is generally also the contract for purchase as well. The offer becomes a binding contract once accepted.