Start-Transcript and output from legacy applications

Is it just me or does the PowerShell transcript only capture output from
the PowerShell output cmdlets?

I have a transcript started and ran uptime.exe against a server and
there was no output in the transcript file!???

If I do this:

uptime MyServer | Write-Output

the output *is* captured to the transcript file. This behavior seems to
apply to any legacy application or scripts.

I can work around this but I was surprised. Can anyone provide some
insight?

--Greg