Invisible background fillings are required?

[sator-imaging]

Hi there,
I realize that material icons SVG has invisible background that is same size to View Box. I'm not sure is there any reason to draw them?

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I've tried to remove it by programmatically for my use but it's so hard. there are many patterns...

# most simple, easily removed by code --> av\volume_down_alt\materialicons\24px.svg
<rect fill="none" height="24" width="24"/>

# some rect has 'x' and/or 'y' attribute --> av\volume_down_alt\materialicons\20px.svg
<rect fill="none" height="20" width="20" x="0"/>

# draw rect by path, simple --> av/videocam/materialicons/24px.svg
<path d="M0 0h24v24H0V0z" fill="none"/>

# some icon draws path from other than top-left corner, and what's this magic number 0.87?
# --> navigation\unfold_less\materialiconstwotone\24px.svg
<path d="M24 0v24H0V0h24z" fill="none" opacity=".87"/>

# drawing rect twice? --> hardware\keyboard\materialiconssharp\24px.svg
<path d="M0 0h24v24H0V0zm0 0h24v24H0V0z" fill="none"/>

# and more patterns, some icon using style instead of fill attribute
<rect style="fill:none" .../>