Online Calender Syncing

Question: Both email and diarl/calendaring programs have been available since the dawn of the 'personal computer'; and yet, whilst email is ubiquitous across all platforms and operating systems, with hundreds of clients to choose between, still we have no real choice and very limited cross-platform compatibility within the calendaring software market. Why?

	WebCalendar	DAViCal	Google Calendar	Chandler	M$ Exchange
	MySQL, PostgreSQL, Oracle, DB2, Interbase, MS SQL, ODBC	PostgreSQL	-	MySQL, (PostgreSQL...)	Proprietory
	vCal,XML,HTML,Free/Busy	.	XML, iCal, HTML, CalDav	CalDAV	(HTML)
Evolution v2.22.3.1 E M A T	Download OK No upload ability	Unknown	Download OK No upload ability	Unknown
Thunderbird v 2.0.0.14 E T
Claws Mail v3.5.0 + vcalendar 2.0	.	.	.	Cannot load: requires username/password	basic functionality
KOrganizer v 3.5.9 E T J	Events :) ToDo's. :)	Unknown	Download OK No upload ability	Download OK Partial upload ability
Chandler v1.0	.	.	.	.	.	Exceptionally Flakey client!
Apple iCal v2.x	.	.	Download OK	.	.
Apple iCal v3.x	.	.	Download OK Upload OK	.	.
Mulberry	.	.	.	.	.	Unable to compile.
M$ Outlook	.	.	+	.	.

+ = Additional Software Required

  E -- Events
  M -- Meetings
  A -- Appointments
  T -- Tasks
  J -- Journal

Standards (what standards???!)

iCAL (RFC2445)
iTIP (RFC2446): iCalendar Transport-independant Interoperability Protocol
iMIP (RFC2447): iCalendar Message-based Interoperability Protocol
iRIP: ICalendar Real-time Interoperability Protocol - Appears abandoned circa. 1999
CAP (RFC4324): Calendar Access Protocol - Obsolete
WebDAV
CalDAV(RFC4791)
GroupDAV: Cut down & simplified version of CalDAV
xCal: An XML-based replacement for iCAL.

Claws Mail & vCalendar plugin: Creation of Meetings only. Unable to set priority. Unable to set privacy.
Chandler Hub: Ignores status, redefines automatically as 'confirmed'.
Chandler Desktop: Unable to set priority. Unable to set privacy.