row – Why the horizontalgauge can not be directly added to the control part of manipulate[]?


I try to use horizontalgauge in Manipulate as following:

    Manipulate[
 Graphics[Disk[]],
 HorizontalGauge[Dynamic[x], {0, 100}]
 ]

but it didn’t work, but if I wrap the gauge with Row[] then it works, can anyone explain why it works like this?

    Manipulate[
 Graphics[Disk[]],
 Row@{HorizontalGauge[Dynamic[x], {0, 100}]}
 ]