@StarbucksFreak,
Some people may be using speaker phones in the mistaken belief that they'll hear better. They may also want someone else in on the call to guide/coach them (think elderly couples in both instances). There are also any number of seniors who have trouble with even the most basic technology. They don't know how to take their phone off speaker because someone else put it on that way (like a grandchild), or they did so months or even years ago and have just plain forgotten how.
I know my cell number, but unless I need to provide it for some form, it's not exactly top of mind. People can also get flustered if they think you want the information
RIGHT NOW (whether you're behaving or sounding that way or not, there are folks who will think that way) so they essentially fumble.
They may also think they're being funny, so chalk that up to some unfunny vamping that some people feel the need to do. It's like having the last name McCoy and someone calling your Dr. McCoy or 'the real McCoy' who thinks they're hysterical but the reality is, you've heard that a million times and it wasn't too funny the first time you heard it. And it sure as hell isn't funny now.
The folks who are moving the phones from mouth to ear and back again are also, likely, seniors, so they are people who started life with tethered landlines. Cell phones feel weird and flat (and probably also feel too light). They can't tuck the phone under their chin or on their shoulder. Consider this: their muscle memory is of physically dialing a phone, tucking it under their chin, and then hanging it up on a switch hook. Every one of these things has changed with cell phones. It can be hard to unlearn those old habits. Keep in mind that, for someone born in 1931 (so they're 90 years old this year),
and who was a late adopter, they my have used landlines (tethered or not. Keep in mind, a lot of cordless non-cell phones have a similar user experience to old tethered landlines) for over 75 years. That's a very ingrained habit, so it can be extremely hard to unlearn.
So, give the elderly a little consideration and patience. You're asking them to do something that's hard for them.