Why guys refuse me for friends with benefits?

Hello everybody
I'm usually very busy and have a little time, maybe one or two days per week (3-4 everything hours approximately) so I'm searching for some casual dating, no strings attached, but guys vanish when something like that needs to happen. I know they like my look, we meet for a coffee to see how we're in live, is there a chemistry and always everything is good, but after I get busy for a week without texting them for the first evening together, they usually ditch me, or they just don't agree for my free days while I give 4 proposals. Why is nobody wants to date casually with me? On the first chat they say they do, but after that they're only writing and chatting which becomes boring for me quickly. If I'm gone for a few days - they're gone too.
This is happening so long, I'm in my 20s while they're near their 30s or early 30s. Tinder is not working looks like. I'd understand if they vanish after night together but they vanish sooner...
What's the trick here, should I act like I wanna relationship so they feel they're cheating on me and be fulfilled or there is something else I should do?
Why guys refuse me for friends with benefits?
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