Why? Because its your idea, remember we have no knowledge of you or your ideas or startup or business. If you want meeting with your targeted software engineer you will have to to do it on their terms, not yours.
It is not that we do not care about your idea, its that you and your idea our strangers. Think of this way startups succeed by having two ingredients the engineer and the salesperson. If the sale of attempting to get an engineer to talk to is so limp and uninteresting that this how the sale presentation before other strangers will be, in other words a complete failure. In other words you are transmitting a sense of failure before you even get started.
For developers the bonding substance usually is a meal. This goes back to the early 1950s and 1960s when computers were slower and thus the talks were self organized around meals while the engineers waited for compiler or console time. Now due to the new build servers and other automates software engineering processes we congregate around a meal while those systems are processing projects.
And you know your startup is in trouble if a software engineer is preaching to you about your lack of social skills. Dale Carnegie's How to Win Friends and Influence People is a good starting place for those who might be new to this.