Test driven development is actually quite uncommon in many parts of the industry.
Sure the startup culture and new breed (new bubble?) tech companies mostly emphasise it, but among older companies it's much less common for a few reasons:
1. It just wasn't considered normal practice until fairly recently.
2. They often use 'lower level' languages, and as @raverbashing mentions, they're more difficult to test.
3. The companies are much slower moving, so arguably have less of a risk with not having automated testing. Automated testing has more benefits in agile than it does in the waterfall methodology.
Sure the startup culture and new breed (new bubble?) tech companies mostly emphasise it, but among older companies it's much less common for a few reasons:
1. It just wasn't considered normal practice until fairly recently. 2. They often use 'lower level' languages, and as @raverbashing mentions, they're more difficult to test. 3. The companies are much slower moving, so arguably have less of a risk with not having automated testing. Automated testing has more benefits in agile than it does in the waterfall methodology.