I met you in a business meeting, or a networking meeting, or in a social group. You’re nice enough, and we had a great talk about the products you’re selling.
You don’t have my trust yet. But I’m interested, enough that I’ll continue the discussions with you. We’ll meet again, and you’d like me to give you leads and referrals.
At some point, I’m still interested, so I’ll go and purchase your product. I appreciate that you were friendly and maybe even gave me a little discount, but I bought it primarily because you were addressing a need that I have.
Ready for me to send you referrals?  Sorry, at most I might mention to a friend, “Yeah, I bought his product once and it seemed OK, and the guy’s friendly enough.” Not exactly a resounding recommendation.
But you actually did a great job – the product and service were great.  I was pretty impressed, and it’s likely that I’ll come back and purchase more from you if I have an appropriate need.
Better yet, if I see someone in the right situation, it’s likely that I’ll tell them about the great experience I had with you. Whether or not I give you their information is a different question – I have to expect that you’re not going to misuse or abuse that privilege.
But now’s the right time for you to ask me about referrals. Remind me that you value and appreciate new business, and tell me how I can best represent you to my friends and colleagues.  It’s been almost a year since we first met, so don’t expect me to remember that first conversation.
And when I send you that referral, make sure I hear a fast “thank you” somehow.  Otherwise, it’ll feel like you’re just using me.
The bottom line: we’re all people who hold our deep trust relationships very closely. It takes time to build those, with repeated contacts.