When you are young and relatively penniless you may have a great need for credit, for instance to buy a car or pay for school or perhaps start up a small enterprise. But, being young and without a lot of credit history, your creditworthiness is not going to be particularly high, making it hard to get good credit.
Fast forward 20-30 years and you earn a good salary, you have perhaps paid off a house, college loans are history, you have savings. Your creditworthiness is great and everyone seems like they would be delighted to give you credit, which you now have no need for.
Time of the day is a little bit like credit -- when you need people to give it to you, no one will. Once it is no longer important to you, everyone is racing to give you some.
I am hosting a visitor next week and I am again reminded how darn hard it is to populate a visitor's schedule. Most often, sending out emails with the abstract and biosketch results in very few people willing to meet the speaker. Then I have to send out individual emails, virtually pulling colleagues by the sleeve to meet with the guest. Other people do it too, and I tend to relent when the host pleads that I see their guest for 30 min.
For most visiting speakers, it's fairly challenging to fill up their day with meetings, and it's hardest when the speaker is a young assistant professor, who actually really needs the exposure that travel brings. Alas, since they are young, no one knows them and no one wants to bestow their precious time on them.
Therein lies the Meet-the-Speaker Paradox: Professor GreyBeard, who is exceedingly unlikely to benefit in any discernible way from visiting your illustrious institution, will have hordes of people wanting to meet with him and shake his hand and tell him how awesome he is and by-the-way-this-is-what-I-do. There will be standing-room only at his talk, even if the talk is incomprehensible/boring/covers really old work. But for young people, whose careers literally may depend on making connections and giving enough of these lectures, it is a real drag getting enough volunteers to populate the schedule. This is the main reason I have become gun-shy about inviting people over to give a talk. I don't want to host too many people in order to avoid wearing thin the patience of those colleagues who kindly agree to most of my meet-the-speaker requests. Having been very disappointed on occasion in the past, when I was the speaker, by very scarce schedules because my hosts didn't want to bother, when I do invite someone these days, I go to great lengths to ensure the speaker is very busy throughout the visit, because busy means appreciated: you feel great at the end of an exhausting day, which you spent talking to many smart people about their science and showing them your own cool work. Maybe the young people's "meeting-worthiness" isn't as stratospheric as a GreyBeard's, but I still like to treat all my guests like it is.