It's because they want to talk to the most power in the decision but with the least information as to how the problem could be solved without the help of Oracle/IBM/whoever.
Best case, they lose control of the narrative as it's reported up internally, and someone higher up still has to approve it.
Worst case, some engineer who actually knows their shit very quickly outlines why this can never work for the given problem.
Once you're into the VP level, there's (usually) less technical knowledge, because folks at that level have full days crammed with higher-level decisions. So it's more plausible for sales to pitch {insert whatever buzzwordy, batshit crazy idea} and have it fly.
[0] (Seminar from 2007) https://youtu.be/rCmvMDrCWjs?t=1919
That didn't always work out. We sold a lot of stuff to Hewlett-Packard and they always forced most of the decisions down to the engineers. They would rarely let us talk to the people who could sign the purchase order. The sales people didn't like it much since they didn't have the control that they were used to. But it was kind of great for all of us technical people because we could sit around with the HP engineers and talk about technical stuff without a lot of sales-speak getting in the way.
The quote I mentioned is just a quote, but it points to a part of a reason. If you are a CEO or a high level executive of a big company, going with IBM or Oracle is a safe bet. It's not very likely you will be blamed for failures of IBM or Oracle. It may be a money hole and bad for business but it's a much safer bet than going with some smaller vendor instead of big name vendors.
Because at some point they might want/need another job, and so often times it's better to help each other out, at the expense of the folks lower down.
Those folks are useless to them, personally, but that VP at Big Vendor probably isn't.