A lot of people (particularly younger ones) don't like the intrusion of a call, and prefer text-based communication.
I don't expect instant replies, but being left on read for ages is rude, IMO. I always reply, and expect replies to texts I send, unless they are obviously statements for info.
Another issue with texts/messengerWhatsApp is that someone has to end a conversation or they go on for ever. The thumbs up emoji can seem dismissive, but not 'signing off' can make people feel that they've been snubbed, or that they are hanging on waiting for a reply. For me, it depends on who I'm talking to. I might just leave a couple of kisses, or say something like 'see you tomorrow', or 'great to catch up - talk soon' if things are dragging on. If it's a close friend/daughter/sister I might be honest and say I'm off now as Happy Valley is starting, or something,