Ok - not having used one of these tabletop frothers, I don't really know how hot they actually get. But I suspect that the difference is down to the steam wand heating the milk more than your frother.
The science behind it (vastly simplified is):
This comes down to how adept you are with a steam wand - initially you don't fully submerge the wand, introducing air into the milk. As it starts to heat, the proteins in the milk "wrap round" the air bubbles. If you do it right, these bubbles are nice and small resulting in "micro foam". You have much more control with a steam wand as opposed to the whisk like implement in frothers.
You'll likely find the bubbles in the froth from your frother are generally larger and thus doesn't last quite as long or look quite as nice as that created by a trained barista in a coffee shop.
The natural sugars (carbohydrates) in the milk break down into "simpler" sugars with heat and enhance the sweetness of the milk. The steam wand introduces more heat and brings the milk to the ideal temperature (with monitoring). For comparison, I have an espresso machine at home, and I get my milk to roughly 70 C
For full details of the science behind it - I found this site which seems to explain it relatively clearly if you're interested in more science detail.