Most BTC is held by an exchange, like Coinbase, Binance, etc... so this statistic is about as meaningful as pointing out that 95% of US dollars are stored at a bank.
A lot of BTC was held by an exchange like Mt. Gox and Bitfinex, too.
With banks I can trust that I can actually get my money bank. BTC isn't decentralised, and the central actors controlling the system are far less reputable (which is saying a lot, when they're being compared to bankers).
So that metric is really bad because almost every Bitcoin wallet only uses each address once, for privacy reasons. Most of those bottom 98% of addresses probably have very small amounts and are just a small part of someones wallet.
An "address" can mean anything - a person can have a wallet with multiple addresses, or an address could belong to an exchange with holds it on behalf of multiple people.
