Is asking employees to wear formal clothing on client visit,
Meaningful to whom?
Clearly it isn't meaningful to you, but is meaningful to whoever in your company requested it.
In my company, we have a "dress code" for most days. In certain periods, the dress code is relaxed. For example, we are currently in a "Casual December". Those of us who have donated money to charity get to wear jeans and sneakers for the month.
But the understanding is that if an important client, or someone important from the home office arrives, we must go back to our normal business casual dress.
Talking to the Sales folks here, they believe it is very important to convey a certain impression to clients and prospective clients. Since more than anything, I want them to bring in a lot of sales so that we can all make a lot of money, I happily go along with it. I help them out in this way, and any other way I can, when revenue is involved.
The part that I don't care for is the dress code for all the non-client-visit days in the year. I see no value in dressing up during the times when clients don't visit. I expect employees to act professionally, and would prefer that we trust them in their dress.
But it's not my company, and I don't make the rules. If it were a huge deal for me, I suppose I would leave. But it's not that important to me, so I just go along with it.