Nop, somehow bitcoin generates good profit margin to investors, Without btc, alt-coins will never evolve in digital world, Bitcoins has also advantages in real world, It is very efficient to use and a good source of income:)
Currently it is not at all efficient to use so you can not say that. Long tx times coupled with large tx fees do not allow it to be used as a daily transaction currency. I am a big proponent of bitcoin and believe these fixes will be enabled but until they are, you should not expect Bitcoin to be used for easy transactions on a widely adopted scale.
As well as your point of a good source of income... How is it a good source of income? If you are talking in a mining aspect then sure if you own 100k worth of hardware you can probably make some money. If you are talking as a purely speculative investment standpoint then I am sure anyone that bought BTC in the last 60 days will probably disagree. I love crypto and know things will rebound but your two points are completely false currently. In long term yes you can probably have a good ROI on your investment but "income" to me means a continual, consistent, and constant source of revenue.
Also yes Bitcoin may have paved the way for other coins and shed light on the blockchain technology. But if you think that it will forever remain on the top than you will probably be upset in the near future. Much more use cases and value in some of the other tokens out there.