A lot. In example:

1) PC Client that synchronize all the conversations, photos, and every other file. So if you send me a file in a conversation by the phone I can use Telegram Desktop and download it directly from PC. (search for Telegram PC client on search engines)

2) Is free to use. Ok some bucks/year aren't a suicide but I have to include also that one.

3) Is veeeery faster than Whatsapp.

4) It is SIM independent, so I can have multiple connection using the same number from my PC, my phone, my tablet and so on.

The problem is that a lot of people stops at "But a lot of my contacts doesn't use Telegram, they use Whatsapp"