Opinions on this topic are diverse and totally depend on an individual. In today's economy, I don't think that spending thousands of money on just one day for someone with whom you reasonably expect to live the rest of your life is unreasonable unless you can afford it. The money is better put towards the first family home. This is not to say that a wedding should not be a Special Day, on which some extra money is spent, but there are many options to make the day special.
Having been to many weddings, two significant costs are unavoidable: Catering and photography. If you cannot afford there's no need for a 5-star catering service, a barbecue gathering with plenty of self-serve foods isn't so expensive, and the left-overs can be frozen for future home-consumption. When choosing a photographer, you want to see samples of previous work, including the bad shots! Sometimes, a friend ends up handing over better photos than the alleged professional, so feel free to ask around for an affordable photographer/friend who is happy to take pictures in exchange for a feed as a guest. The memories of sharing that time with your friends will be far more critical than any expense that was over-looked.
On the other hand, it is okay to spend a lot of money if you have money. A wedding isn't just a party, and it is a form of gratitude you show to your closest friends and neighbors because you have found the love of your life. The one that will replace the role of your mother or father to take care of you for the rest of your life. It is also evidence of how big your love to your partner is, how big your effort to make them happy is, how big you appreciate him/her in front of his/her relations and colleagues. Again, a wedding isn't just a party, it is the beginning of your love life, and I believe that you certainly want it to be beautiful as a reflection of your love life after marriage.
There are some religious beliefs that a wedding is an obligation. Its function is to deliver a message to people around you that you've been married. Therefore, it is okay for you and your partner to live in one roof and do a marital relationship. A prestigious wedding could also be a proof to your partner's parents that you are worth enough to take their children out of their homes because you are wealthy enough. A wedding highly depends on your circumstances.
A wedding is not for you, the bride/groom, it's for your guests. They're the ones with the time and leisure to enjoy everything. They get to actually taste the food, dance, drink, and generally experience all the stuff you poured your money and time into setting up. The only thing you get out of it is months of planning and stress, just to end up in the exact same place you would have been had you, your parents, and a couple of friends, taken care of this in front of the Attorney General's office in a private/small event–legally married.
For generations, weddings were small affairs. The whole thing of big white dresses, massive cakes, bands, DJs, and all of that came about as nothing more than a pissing contest between rich people trying to show their wealthy friends how rich they are. And these days, you have magazines, TV shows, social media, and all that trying to tell you that if you don't have the perfect dress, the ideal venue, the perfect cake, the perfect playlist for your reception, the excellent professional photographer, your entire marriage will be doomed. There's no relationship between the amounts of money spent on getting two people married and the likelihood that marriage will last, so keep it affordable.
Weddings have an exciting role in people's lives; they simultaneously provide a way to commit your love to each other before witnesses, provide one of only a couple times where families and friends feel obligated to congregate and provide an opportunity for an entertaining party for you and your spouse.
If anything, a wedding is going to be expensive; it's probably not worth going into debt for a wedding that you can't payback. Find a creative way to celebrate. If your friends and family come, they'll make the commitment special anywhere it happens. Spend what you can afford, remembering that it is stressful to continue paying for the wedding after it is over. No one will remember all the things that the wedding industrial complex will tell you that you need. They will remember if everyone was happy to be there. Finally, having or not having a wedding totally depends on where you are in your life.