Of course a heavy steel bike is heavier than a light aluminium bike...
...but a heavy aluminium bike is heavier than a light steel bike as well !
Even 10 years ago, cheaper bikes were steel, aluminium was more expensive, titanium was mega-megabucks and carbon stratospheric.
Because they're more shock and particularly vibration absorbent, steel and titanium are frequently used for touring and audax bikes, rather than harsher aluminium or fragile carbon.
But for road-race bikes or MTB's, manufacture and construction of aluminium frames in Taiwan and China means that aluminium is today comparatively a lot cheaper than it was and it's now the norm for starting-level enthusiast road race bikes or MTB's from Specialized, Trek, Giant, etc.
Yes, really, really cheap rubbish bikes (the £59.99 from Argos MTB type stuff) are really heavy steel (usually sold as 'high-tensile', not even as Chromoly or other alloys), but the norm for an aimed-at-enthusiasts bike is aluminium these days rather than steel.
If an enthusiast is riding a steel road bike, it's usually a more expensive, low-volume or frequently custom bike, using 653 or another exotic alloys, which will be more expensive than the mass-production aluminium bikes and perhaps lighter too.
Carbon has come down in price too, as a spin-off from its greater use in aerospace, sportscar, etc applications, and off-the-peg full-carbon bikes can be had for about a grand - but again you can get lighter weight but more expensive exotic aluminium or steel frames.