Certainly take your point about the need for accessibility and availability - but there is a but.
It is entirely possible to be 'available' by email (which should be a dotgov account), by mobile and / or landline and via social media at an individual councillor level as well as the collective 'correspondence in' facilities of the corporate council.
All of that being said, there are (at least) 2 important factors to consider:
(1) personal and online security - notably home addresses - must always be at the individual discretion. Scammers, ne'er-do-wells and those with a grievance have more than enough opportunity to harvest online info without giving them additional data.
(2) mindful of course that (PCs) are entirely voluntary, there should also be some degree of control over how, when and why one might choose to take individual queries - many councillors will have work, home and social commitments that simply don't facilitate 24/7 access.
I do take your point about availability and accessibility and I do share your apparent passion for it, but my enthusiasm is constrained by certain realities.
What we should all perhaps strive for is greater public interest and attendance at PC meetings.