Creating Flex applications without MXML but with AS3

Question

To me it seems logical that if I want to build an application
I should use AS3 to create reusable components, classes, the
layout, etc.
.. however, searching around on the web I exclusively find
Flex tutorials and examples using MXML. This is also true for the
books (e.g. Adobe Flex 2 - Training from the source") -- why is
this?
Is it wrong of me to think it'd be best to create everything
in AS3? Do anyone have links to tutorials etc. where they use AS3
to build Flex applications?

Answer 1

Although I have not seen tutorials about this I did create a
test app using the following approach:
<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas xmlns:mx="
http://www.adobe.com/2006/mxml"
xmlns:lib="components"
width="100%"
height="100%"
creationComplete="initGrid()"
scroll="false"
>
<mx:Script>
<![CDATA[
..... AS 3 code here to create/populate app - datagrid in my
case
]]>
</mx:Script>
<mx:VBox id="_box" width="100%">
<mx:Button id="hideShowCols" label="Hide Empty Columns"
click="doColumnAction();"/>
<mx:DataGrid id="delinquenciesGrid"
alternatingItemColors="[#cce6ff, #e8ffff]"
alpha="0.5"
lockedColumnCount="3"
allowMultipleSelection="true"
rowCount="20"
headerColors="[#cccccc]"
fontFamily="Arial"
visible="false"
preinitialize="detectClick();"
>
</mx:DataGrid>
</mx:VBox>
</mx:Canvas>
Even the data grid does not need to be "declared" in MXML, it
was just a faster way to do it for me - you could do
canvas_id.addChild(...) any element/item that you create in
AS3.... or in my case i was doing _box.addChild(newGrid)