Bitcoin is old but Pi is new. Owning a Pi in the next 3-5 years is necessary because:

1. Potential for price increase: Pi is a new cryptocurrency, if widely applied, the value can increase significantly.

2. Easy to access: Pi can be mined for free via mobile applications, suitable for beginners.

3. Cryptocurrency trend: As cryptocurrencies become a global trend, owning Pi helps you participate early in the potential market.

4. Developing community: Pi has a large and growing user community, creating opportunities for cooperation and learning.

5. Security and decentralization: Pi is designed to be secure and decentralized, in line with modern financial trends.

In short, owning Pi is an early approach to cryptocurrencies, providing investment opportunities and participating in the future of finance.