Yes, it is necessary NOW - to avoid issues like BTC (fees + clogging) and ETH (clogging) in the future
It's pretty easy to run a pruned BCH node - you can choose how many GBs of history you want to maintain on your node. BCHD is working on utxo commitments - that'll allow people to spin up new nodes with just the unspent outputs.
That said, fees will go up when the network reaches its limits. But the fees won't go up so much or so quickly if we have a high capacity. It's like adding a gallon of water to a reservoir (BCH), the level doesn't rise much, but try adding the same gallon to a puddle (BTC)!
Generally we want to increase transactions as much as possible to find the limit that the BCH network can operate at without degrading - it's only then that we can be see if the limits are increasing. There's an old adage - 'You get what you measure' - well we want increased real capacity so we need to measure real capacity - and can we do that by using the network to the max - and we don't do that by coddling the network.