You wouldn't give the keys to your Mercedes Benz to your child, just as God doesn't give something as important as keys to hell or the kingdom to a new believer. And imagine the mayhem if everyone had a key. Only specially chosen individuals get keys. And they also have the added responsibilty and accountability which goes with having it.
Notice Jesus is speaking specifically to his disciples. This is in connection with the previous verse which you can see is about resolution of grievances and telling them to the church etc.
Binding and loosing has nothing to do with spiritual warfare (eg exorcism),
the terminology for binding and loosing was applied to accepting or rejecting which doctrines were true and which were false. It may also be applied to the power and authority to excommunicate people from the church. As apostles in the church this was the job given and we see them use their authority to declare the true Gospel, and deal with severe sin on a number of occasions.
If we look up Gill commentary on the bible for example, it says:
This also is not to be understood of binding, or loosing men's sins, by laying on, or taking off censures, and excommunications; but only of doctrines, or declarations of what is lawful and unlawful, free, or prohibited to be received, or practised; in which sense the words, אסור ומותר, "bound and loosed", are used in the Talmudic writings, times without number, for that which is forbidden and declared to be unlawful, and for that which is free of use, and pronounced to be so: in multitudes of places we read of one Rabbi אוסר, "binding", and of another מתיר, "loosing"; thousands, and ten thousands of instances of this kind might be produced; a whole volume of extracts on this head might be compiled. Dr. Lightfoot has transcribed a great many, sufficient to satisfy any man, and give him the true sense of these phrases; and after him to mention any other is needless; yet give me leave to produce one, as it is short, and full, and explains these phrases, and points at the persons that had this power, explaining Ecc_12:11 and that clause in it, "masters of the assemblies".