The reasons why so many persons invest in bitcoin is the depreciation, centralization and the appreciative aspect in bitcoin.
What are your source of learning about bitcoin which states it's centralised in the first place? If you have studied it properly then you must have understood that it's the first decentralised cryptocurrency that made it possible for us to have that financial freedom providing us alternative to the central monetary system and many more things.So if you say it's centralised then it's all wrong and it's completely decentralised in all the ways like no there is no main server, institutions,mining pools controlling it.
Even if we see it from Mining aspect then after the China ban the hashtate distribution has increased to different parts and there are many pools so nobody have the central chain of authority over it
So then you said about appreciation and depreciation then it's termed as bitcoin volatility and prices fluctuate on the simple rule of economics which is demand and supply so at this time people are dumping the coins and FUD is there which is pushing price graphs downward but if you have known btc for a while then you must understand it tends to grow in the long run as there is mass adoption on the line with supply shrinking.
This stages are very important to traders or exchangers. it’s a medium of efficient, crypto currency has been a life change in recent years, it has been a great value for storing assets, commodities and currency. These qualities attract to those who believe In future bitcoin. Crypto help those who have issues with hyperinflation..
Crypto market is big and there are thousands of coins trading over exchange and more than 18k listed on CMC so do you believe all of them are are like bitcoin? I would say none of them is like it and many people beleive it to be get rich scheme but are rugged by scam projects with shitcoins.The other coins are different but only bitcoin is good hope for us to deal with hyperinflation and if you know this fact then you how risky the market is.
People investing in bitcoin are of two categories like the first one is to make quick profits seeing prices rises in bull run but when it drops they panic sell contributing worse to the situation
The second category is people who understand bitcoin at core level and realise true financial freedom against government and with profit they can also gain in the long run.