Because every modern chat application allows for more than text chat. Sure the name is 'text chat' so you can take that literally and say "if it allows you to send text its text chat". Its like a phone, if I say here is a phone and hand someone a landline they're gonna be like wtf.

I see this all the time with IRC, people will say lets move to IRC and the discord users will use irc for 5 mins and say its shit because its missing every single basic feature let alone the ones that actually make a platform enticing.