I wouldn't say they were outdated as they are still useful for offline business. A little overlooked and underrated definitely but not outdated because they still have a use today and still required by a lot of big companies. You can tell someone about your website, email address or contact number, but when its put down on a business card they don't have to remember it as its on the card. They just have to remember where they put it!
When they want to use your business or contact you for something. Of course most people just Google it, know it or save it to their phone but when all those things fail, the small cardboard business card is always there. Provided they can remember where they put it!
They're really good little things for drumming up offline business really. When you're out and about, on business meetings etc and you meet new people or start talking about your business you can just hand them one of your business cards. Most entrepreneurs and business minded people have them, or at least, a bunch of them in their wallet/briefcase.
I've used them in the past to promote businesses. By leaving them in shop windows, on counter tops in shops that were related to my business (which was a mobile business so most mobile repair shops in my area). That might just involve asking them if that's okay to leave some there in a holder and if its related to their business most will say fine where as some might want something for it.
Obviously you gotta pay for advertising sometimes even if its just leaving business cards somewhere. I used to leave them everywhere, pubs, clubs, peoples cars, on the bus/train, everywhere. I'd say about 20% of them drummed me up some business but as said I used to leave them everywhere and in shop windows, counter tops etc.
So yes business cards can still be effective. Useful and handy too. But it's just one part of your offline/online advertising and branding.
I think you can get like 1000 from Vistaprint for about 5 bucks so pretty reasonable too.