Bitcoin is the only coin you can buy without significant risk of falling for a scam, compared to other coins, especially for people who are just getting familiar with cryptocurrencies. Just look at whats happening with altcoins right now. In a market like this, its very easy to lose faith, but this doesnt apply to Bitcoin. Its doing great and is even very close to its all-time high, so the choice is obvious.
I do recommend newbies to invest in bitcoin alone because of the risk involved in other altcoins. We have seen different altcoins fall in the past, but whenever you tell newbies to invest in bitcoin rather than altcoins, they dont always like the idea because they feel bitcoin price is already high, or they wont be making much money from bitcoin any longer, they prefer to invest in shitcoins, coins that will be able to multiply their money within a short period of time, and they dont even think about the risk involved in it, and the funniest part is that most of them are always losing money instead of making money.
Bitcoin investment is the only coin which I know if you can hold for long term, then you are going to be making profit, and after investing you going to be having peace of mind because I will say the highest that do happen is that bitcoin will dump, and if you can hold, then we should always expect a bounce back.