Short answer: Due to economical and technological reasons.

Long answer: If you are negativelly biased towards Ethereum then you are a simple minded, ignorant person. Usually those are the ones that believe in cults, religions and have no oppinion of their own. These people are not the kind of people that drive the world forward. Bitcoin is not only about one specific blockchain. Bitcoin is an idea. A technological revolution. Like the fire. Like the wheel. Like electricity. Like the internal combustion engine. Like the internet. The genious idea and endless applications that can evolve out of it cannot be limited to a single chain. Vitalik originally wanted his ideas on Bitcoin. Seeing that the specific ecosystem is not flexible enough to develop quickly enough to incorporate his ideas, he decided to make a new blockchain. A different one. A better one. In nature this is called evolution. He then proposed his whitepaper and EVERYONE was invited to the party. With as little as 1 dollar invested back in the ICO you'd have good pocket money today. The thing is there were certain "religious" blind people that think the only way to go is Bitcoin. WRONG. The blockchain will produce many more ideas like Bitcoin, Ethereum and others. Ethereum will for sure one day have 10 times the marketcap of Bitcoin. Bitcoin could still cost 100k. Who knows - maybe there will  be an even better crypto, to emerge out of nowhere and overtake both. As of today Ethereum is more secure, more decentralized, with better governance, faster, cheaper, with far more capabilities and huge potential. Don't mistake my trust in it with fanatism. I own bitcoin and bitcoin is fantastic. I own ethereum and ethereum is even better. Both can fail. However the future looks a little brighter for ethereum, considering bitcoin is in a political nightmare right now.

Cheers