Likely the bulbs you were replacing on the dimmed fixture were noticably
blackened. The envelope must be kept very hot to keep tungsten vapor from
depositing on it. Which is why the bulbs are very small so they are close
to the filament and get hot. A regular glass bulb must be a minimal size
for a given wattage to keep from melting. Since a halogen bulb must stay
very hot to work properly it's small and is made of blown quartz instead of
glass, hence one of the old names was quartz-iodide.