For almost 35 years a controversy has raged over whether or not the Viking LR experiment detected life on Mars. Although the results of the LR experiment met the pre-launch criteria for the detection of life, the dominant explanation of the results was that a superoxide in the soil was responsible for oxidizing the organic molecules in the LR nutrient.

I can't believe I missed this article. After a quick read, it doesn't seem that ridiculous.

What I don't understand, is why the Mars Rover missions didn't have life-detecting apparatuses?

Luckily Mars Curiosity Rover is going to detect whether or not methane or CO2 in the atmosphere has chemical or biological origins.

Here is a good paper about it.

Regular measurements over the course of the two-year landed mission will provide better temporal resolution than the presently sparse ground-based measurements. As extensive terrestrial field work has illustrated (Sherwood Lollar et al., 2006), a broad range of measurements will ultimately be required to definitively prove if the source of methane on Mars is biotic or produced abiotically by processes such as serpentization.

I just hope it survives that crazy-ass entry sequence.