and one of them is IT investment
Why ? Because its benefit is intangible and people tend not to invest in something that they can't really see how it can help them.
You can send and receive emails everyday, you take it for granted. You don't see it as a result when you invest in proper infrastructure and hire a good network engineer
You read the sales report everyday, you take it for granted. You don't see as a result when you invest in a proper report system and you train your data importer well enough
Even for myself, I usually find it hard to quantify the projects I deployed. I can't really say it helps to increase sales. How much ? Is it really because of that project, or is it seasonal, or is it because of the sales team only ?
So, the first step to take when you want to get your IT investment approved is to show exactly how it helps. Get people to realize the benefits and believe in it.
IMO, the second thing is to show them the potential loss without proper IT investment. To make them realized what they haven taken for granted.
It will be tough since this is something 'bout the mindset.
That's why it's interesting.