But altcoins also has safer investment like those who are listed in top 10 currencies.
Okay so you believe all that are in top 10 on CMC are safe investment? They have doge at number #10 and how much safe you consider it and another centralised coin XRP at #8 who has managed to stay under $1 for long period of time and many other which does not have future guarantee that whether they will be in top 10 or not so how do you call them safe in regards to bitcoin who has given so much returns to the holders.
Bitcoin is the safest of course because of the Huge support and high demand but remember that altcoins also promise more support and benefits.
Wrong bitcoin is not safe due to huge demand but it is safe due to full nodes and the miners and it's complete decentralisation as the demand is totally another factor and those altcoins you are talking about have not much nodes and security could be compromised any time or the centralised wallets could take over the market to create dump like situation as most of them are low priced.So not much of security in them as well.
remember also that in Congestion we use altcoins instead of Bitcoin because of the High fees from the miners that cost us a lot and make us turn at altcoins for a while.
Fees is main concern for many but have you seen the gas at this time as they cost much more then bitcoin and sometimes memepool is empty of which you can take advantage of and pay less than usual but it's really not a big problem if you take it as an investment rather than making more transactions on daily basis.You can check out it here in detailed view in thread by LoyceV :
[Dec 2021] Mempool empty! Use this opportunity to Consolidate your small inputs!Don't get bitcoin if you don't want but make some clarification on your basis as i also got it late and now btc is my best option mate.