"You play with the fish."
अनुवाद:तुम मछली के साथ खेलते हो।
Yes, the same issue with 'वह' and 'वे' becoming 'वो' colloquially. वो is incorrect per grammar.
Another thing to point out here is 'fish' in English can be singular and plural both.
"The fish is swimming" is used when one fish is swimming.
"The fish are swimming" is used when several same kind of fish are swimming.
Also, "The fishes are swimming" is used when several different kinds of fishes are swimming.
With this in mind "तुम मछलियों के संग खेलते हो" or "आप मछलियों के संग खेलते हैं" are also correct translations.
I totally agree about the ingraining of 'वो'. There is another reason: poetic and musical licence. You will not find वह used in Bollywood (Or should it be Mollywood after the name change?). It has two syllables and is not musical.
Think about these two grammatically correct versions: "वे चुप रहें तब मेरे दिल के दाग़ जलते हैं" or "वह शाम कुछ अजीब थी".
They sound very odd. Don't they? The lines used in those songs were the colloquial forms: "वो चुप रहें तो मेरे दिल के दाग़ जलते हैं" and "वो शाम कुछ अजीब थी".
Having said that, I agree, when learning, it is good to learn the right way and as one goes deeper, nuances such as these can be learned.
One of the reason is that India is movie loving country and hindi movies are made by people from different states.(rajasthan,up,bihar,maharastra,madhya pradesh,jharkhand,gujarat e.t.c)All states have their own language with hindi.
In some languages like rajasthani e.t.c वो is वह.
For e.g.,वो कुन है। in hindi वह कौन है।
Please comment to support my comment.