There is utility in being able to evolve the protocols without giving up the integrity of the previous version. Eth2 isn't a different currency, it's a replace

There is utility in being able to evolve the protocols without giving up the integrity of the previous version. Eth2 isn't a different currency, it's a replacement system that links with Eth1 to provide continuity. The ETH coins are not being replaced; both systems transact in ETH and are linked. That's why they are being careful with how it's evolved and how the economic links and incentives, and smart contracts and data sources, are set up in the transition. There are many changes being implemented through this evolution. From PoW to PoS, single chain to cross-linked sharding (while managing the incentives to maintain the integrity of the network), various improvements to faster synchronisation, lower storage requirements, distributed storage of the state. Being able to release v2, v3, v4 of software while staying compatible with all the work you did using v1 is a good thing. Same idea with evolving Ethereum. Contrast it with the numerous new coin networks that use newer cryptographic ideas but each start their own separate networks. That's also evolution, but they don't provide continuity in the same way; instead they are a series of competing products.