In deed, to this writer's knowledge, crude buyers, particularly the more established and prominent ones, would very rarely offer an LOI upfront to any sellers to initiate a purchase. And when, especially, the supposed "seller" that's involved is one that is a virtual unknown to the buyer, or one that is merely an Internet_generated seller about whose bona fides and credentials the buyer knows practically next to nothing, one can be almost absolutely certain that the chances of a crude buyer of substance signing over an LOI to such a seller, is practically next to zero.
If you are dealing directly with sellers to buy properties, rarely will you need to use a letter of intent. Instead, you'll be meeting with them in person to sit down and discuss options for buying their property. However, if you are working through a real estate agent (or two real estate agents if you're not dealing with the listing agent directly), letters of intent can help you succinctly express your offer in the best light, especially when you don't know if the agent who will be presenting your creative offer will understand the full benefits of it.