Technical pre-sales is a crucial function in selling many business-to-business solutions. The pre-sales function is often selling trust to the client; the client needs to know that "the thing" will happen if they buy the solution. Most importantly, they need confidence it will happen on-time and on-budget.
This is a huge part of the cycle - many sales people simply do not have the depth of knowledge that is required to talk in great detail about the minutiae of a technical solution but this knowledge is essential to a successful project.
As with nearly all meetings, the client will likely search for the individuals that are coming to a pre-sales meeting; if they find the profile of an individual who is "all over" a subject, that will markedly improve their sense that all will be well if they choose that vendor.
There is an old saying in sales that “People buy People”, this hasn’t changed, in fact in the Social world this is more appropriate. Assuming you are a Pre-Sales person that wants to be recognised as a Professional in your industry, are interested in what you do and what to win your bonus; you need to wake up to Social Selling