Think there's no 'fix' simply because that's the default display behaviour
for embedded sheet objects. The sheet tabs will show (amongst other usual
excel user interfaces) only when you double-click on the sheet object to go
into edit mode in excel .
If what you're after is to display everything as-is from excel in powerpoint
for a particular sheet view, try a screen dump, viz:
a. With the desired excel sheet on-screen, press Print Screen key
(this copies the screen to clipboard)
b. Toggle over to powerpoint and paste. Resize the bitmap image to fit the
slide.
The only downside, unlike embedded sheet objects, is that you can't edit the
bitmap image directly in powerpoint.