Why do most people choose to use WhatsApp over telegram??

Telegram's official components are open source, with the exception of the server which is closed-sourced and proprietary.

Telegram was launched in 2013 by the brothers Nikolai and Pavel Durov. Previously, the pair founded the Russian social network VK, which they left in 2014, saying it had been taken over by the government. Pavel Durov sold his remaining stake in VK and left Russia after resisting government pressure.

Telegram is registered as a company in the British Virgin Islands and as an LLC in Dubai. It does not disclose where it rents offices or which legal entities it uses to rent them, citing the need to "shelter the team from unnecessary influence" and protect users from governmental data requests. After Pavel Durov left Russia in 2014, he was said to be moving from country to country with a small group of computer programmers consisting of 15 core members. While a former employee of VK claimed that Telegram had employees in Saint Petersburg, Pavel Durov said that the Telegram team made Berlin, Germany, its headquarters in 2014, but failed to obtain German residence permits for everyone on the team and moved to other jurisdictions in early 2015. Since 2017, the company has been based in Dubai.

Session is another good alternative that doesn't require a phone number

Yeah, I'm with you. Plus no end to end encryption. Go ahead and let Russia see all your messages.

Telegram was banned in Russia.

Stop spreading misinformation troll.

the guy who created it was born in russia... but pissed off russian authorities and i don't think he can set foot in russia anymore without being arrested

Most people don't care about privacy anyways so in this case I'd argue features are more important for the average user, which telegram has.